diff --git a/piker/ui/_chart.py b/piker/ui/_chart.py
index a39365c7..a9223035 100644
--- a/piker/ui/_chart.py
+++ b/piker/ui/_chart.py
@@ -1427,6 +1427,10 @@ async def run_fsp(
         period=14,
     )
 
+    async def settings_change(key: str, value: str) -> bool:
+        print(f'{key}: {value}')
+        return True
+
     async with (
         portal.open_stream_from(
 
@@ -1445,7 +1449,8 @@ async def run_fsp(
         # TODO:
         open_form_input_handling(
             sidepane,
-            focus_next=linkedsplits.godwidget
+            focus_next=linkedsplits.godwidget,
+            on_value_change=settings_change,
         ),
 
     ):
@@ -1538,14 +1543,14 @@ async def run_fsp(
 
         done()
 
-        i = 0
+        # i = 0
         # update chart graphics
         async for value in stream:
 
             # chart isn't actively shown so just skip render cycle
             if chart.linked.isHidden():
-                print(f'{i} unseen fsp cyclce')
-                i += 1
+                # print(f'{i} unseen fsp cyclce')
+                # i += 1
                 continue
 
             now = time.time()
diff --git a/piker/ui/_forms.py b/piker/ui/_forms.py
index 7263d7b8..c4a05c77 100644
--- a/piker/ui/_forms.py
+++ b/piker/ui/_forms.py
@@ -363,7 +363,7 @@ async def handle_field_input(
 
                 key = widget._key
                 value = widget.text()
-                await on_value_change(key, value)
+                on_value_change(key, value)
 
 
 def mk_form(
@@ -539,8 +539,8 @@ def mk_fill_status_bar(
     # PnL on lhs
     bar_labels_lhs = QVBoxLayout(fields)
     left_label = fields.add_field_label(
-        dedent(f"""
-        -{30}% PnL
+        dedent("""
+        {pnl}% PnL
         """),
         font_size=bar_label_font_size,
         font_color='gunmetal',
@@ -567,16 +567,17 @@ def mk_fill_status_bar(
     # https://docs.python.org/3/library/string.html#grammar-token-precision
 
     top_label = fields.add_field_label(
-        dedent(f"""
-        {3.32:.1f}% port
+        # {limit:.1f} limit
+        dedent("""
+        {limit}
         """),
         font_size=bar_label_font_size,
         font_color='gunmetal',
     )
 
     bottom_label = fields.add_field_label(
-        dedent(f"""
-        {5e3/4/1e3:.2f}k step\n
+        dedent("""
+        x = {step_size}\n
         """),
         font_size=bar_label_font_size,
         font_color='gunmetal',
@@ -665,7 +666,7 @@ def mk_order_pane_layout(
     # _, h = form.width(), form.height()
     # print(f'w, h: {w, h}')
 
-    hbox, fill_bar, left_label, bottom_label, top_label = mk_fill_status_bar(
+    hbox, fill_bar, left_label, top_label, bottom_label = mk_fill_status_bar(
         form, pane_vbox=vbox
     )
     # TODO: would be nice to have some better way of reffing these over
diff --git a/piker/ui/_interaction.py b/piker/ui/_interaction.py
index d65bbc22..022566d4 100644
--- a/piker/ui/_interaction.py
+++ b/piker/ui/_interaction.py
@@ -262,12 +262,9 @@ async def handle_viewmode_kb_inputs(
             # hot key to set order slots size
             num = int(text)
             pp_pane = order_mode.pane
-            pp_pane.alloc.slots = num
-
+            pp_pane.on_ui_settings_change('slots', num)
             edit = pp_pane.form.fields['slots']
-            edit.setText(text)
             edit.selectAll()
-
             on_next_release = edit.deselect
 
             pp_pane.update_status_ui()
diff --git a/piker/ui/_position.py b/piker/ui/_position.py
index be1ef1fe..d5190b33 100644
--- a/piker/ui/_position.py
+++ b/piker/ui/_position.py
@@ -35,6 +35,7 @@ from ._anchors import (
     pp_tight_and_right,  # wanna keep it straight in the long run
     gpath_pin,
 )
+from ..calc import humanize
 from ..clearing._messages import BrokerdPosition, Status
 from ..data._source import Symbol
 from ._label import Label
@@ -77,13 +78,17 @@ SizeUnit = Enum(
 
 class Allocator(BaseModel):
 
-    symbol: Symbol
-
     class Config:
         validate_assignment = True
         copy_on_model_validation = False
         arbitrary_types_allowed = True
 
+        # required to get the account validator lookup working?
+        extra = 'allow'
+        # underscore_attrs_are_private = False
+
+    symbol: Symbol
+
     account: Optional[str] = 'paper'
     _accounts: bidict[str, Optional[str]]
 
@@ -108,6 +113,21 @@ class Allocator(BaseModel):
     currency_limit: float
     slots: int
 
+    def step_sizes(
+        self,
+    ) -> dict[str, float]:
+        slots = self.slots
+        return {
+            'units': self.units_limit / slots,
+            'currency': self.currency_limit / slots,
+        }
+
+    def limit(self) -> float:
+        if self.size_unit == 'currency':
+            return self.currency_limit
+        else:
+            return self.units_limit
+
     def next_order_info(
         self,
 
@@ -127,12 +147,17 @@ class Allocator(BaseModel):
         live_size = live_pp.size
         startup_size = startup_pp.size
 
-        step_size = self.units_limit / self.slots
-        l_sub_pp = self.units_limit - live_size
+        steps = self.step_sizes()
 
-        if self.size_unit == 'currency':
+        if self.size_unit == 'units':
+            # step_size = self.units_limit / self.slots
+            step_size = steps['units']
+            l_sub_pp = self.units_limit - live_size
+
+        elif self.size_unit == 'currency':
             startup_size = startup_pp.size * startup_pp.avg_price / price
-            step_size = self.currency_limit / self.slots / price
+            # step_size = self.currency_limit / self.slots / price
+            step_size = steps['currency'] / price
             l_sub_pp = (
                 self.currency_limit - live_size * live_pp.avg_price
             ) / price
@@ -184,18 +209,19 @@ class OrderModePane:
 
     def on_selection_change(
         self,
-        key: str,
+
         text: str,
+        key: str,
 
     ) -> None:
         '''Called on any order pane drop down selection change.
 
         '''
-        print(f'{text}')
+        print(f'selection input: {text}')
         setattr(self.alloc, key, text)
-        print(self.alloc.dict())
+        self.on_ui_settings_change(key, text)
 
-    async def on_ui_settings_change(
+    def on_ui_settings_change(
         self,
 
         key: str,
@@ -205,7 +231,56 @@ class OrderModePane:
         '''Called on any order pane edit field value change.
 
         '''
-        print(f'settings change: {key}:{value}')
+        print(f'settings change: {key}: {value}')
+        alloc = self.alloc
+        size_unit = alloc.size_unit
+
+        # write any passed settings to allocator
+        if key == 'limit':
+            if size_unit == 'currency':
+                alloc.currency_limit = float(value)
+            else:
+                alloc.units_limit = float(value)
+
+        elif key == 'slots':
+            alloc.slots = int(value)
+
+        elif key == 'size_unit':
+            # TODO: if there's a limit size unit change re-compute
+            # the current settings in the new units
+            pass
+
+        elif key == 'account':
+            print(f'TODO: change account -> {value}')
+
+        else:
+            raise ValueError(f'Unknown setting {key}')
+
+        # read out settings and update UI
+
+        suffix = {'currency': ' $', 'units': ' u'}[size_unit]
+        limit = alloc.limit()
+
+        # TODO: a reverse look up from the position to the equivalent
+        # account(s), if none then look to user config for default?
+        self.update_status_ui()
+
+        step_size = alloc.step_sizes()[size_unit]
+
+        self.step_label.format(
+            step_size=str(humanize(step_size)) + suffix
+        )
+        self.limit_label.format(
+            limit=str(humanize(limit)) + suffix
+        )
+
+        # update size unit in UI
+        self.form.fields['size_unit'].setCurrentText(
+            alloc._size_units[alloc.size_unit]
+        )
+        self.form.fields['slots'].setText(str(alloc.slots))
+        self.form.fields['limit'].setText(str(limit))
+
         # TODO: maybe return a diff of settings so if we can an error we
         # can have general input handling code to report it through the
         # UI in some way?
@@ -216,7 +291,7 @@ class OrderModePane:
     ):
         alloc = self.alloc
         asset_type = alloc.symbol.type_key
-        form = self.form
+        # form = self.form
 
         # TODO: pull from piker.toml
         # default config
@@ -261,16 +336,7 @@ class OrderModePane:
 
             limit_text = alloc.units_limit
 
-        # update size unit in UI
-        form.fields['size_unit'].setCurrentText(
-            alloc._size_units[alloc.size_unit]
-        )
-        form.fields['slots'].setText(str(alloc.slots))
-
-        form.fields['limit'].setText(str(limit_text))
-
-        # TODO: a reverse look up from the position to the equivalent
-        # account(s), if none then look to user config for default?
+        self.on_ui_settings_change('limit', limit_text)
 
         self.update_status_ui(size=startup_size)
 
@@ -289,7 +355,7 @@ class OrderModePane:
             prop = live_currency_size / alloc.currency_limit
 
         else:
-            prop = size or live_pp.size / alloc.units_limit
+            prop = (size or live_pp.size) / alloc.units_limit
 
         # calculate proportion of position size limit
         # that exists and display in fill bar
@@ -325,14 +391,6 @@ class OrderModePane:
         order.price = level
         order.size = order_info['size']
 
-    def on_settings_change_update_ui(
-        self,
-    ) -> None:
-        # TODO:
-        # - recompute both units_limit and currency_limit
-        # - update fill bar slotting if necessary (only on slots?)
-        ...
-
 
 class PositionTracker:
     '''Track and display a real-time position for a single symbol