This one is good:

<?xml version="1.0" encoding="UTF-8"?>
<instant>
  <Main x="209" y="118" w="3307" h="1928" current-tab="editor"/>
  <Editor id="31" edit-horizontal-pane-pos="0.89999997615814209" notebook-shrunk="0" edit-vertical-pane-pos="0.89999997615814209" mixer-width="Wide" zoom-focus="ZoomFocusPlayhead" zoom="2048" snap-to="SnapToBeat" snap-mode="SnapOff" internal-snap-to="SnapToBeat" internal-snap-mode="SnapOff" pre-internal-snap-to="SnapToBeat" pre-internal-snap-mode="SnapOff" edit-point="EditAtMouse" visible-track-count="-1" playhead="0" left-frame="0" y-origin="0" show-measures="1" maximised="0" follow-playhead="1" stationary-playhead="0" region-list-sort-type="ByEndInFile" mouse-mode="MouseObject" join-object-range="0" show-editor-mixer="1" show-editor-list="1" editor-list-page="1" show-marker-lines="0" nudge-clock-value="220500">
    <Window name="Editor" visible="0" x-off="-1" y-off="-1" x-size="-1" y-size="-1" tabbed="1"/>
    <Buttons>
      <Press/>
      <Release/>
    </Buttons>
    <Selection/>
    <RegionList sort-type="ByEndInFile" sort-ascending="1" show-all="0" show-automatic-regions="1"/>
    <ActionScript lua="Lua 5.3">c2NyaXB0cyA9IHt9IA==</ActionScript>
    <ActionHooks/>
    <EditorLocations clock-mode="BBT"/>
  </Editor>
  <Mixer mixer-rhs-pane1-pos="0.60000002384185791" mixer-rhs-pane2-pos="0.69999998807907104" mixer-list-hpane-pos="0.20000000298023224" mixer-inner-pane-pos="0.80000001192092896" narrow-strips="0" show-mixer="0" show-mixer-list="1" maximised="0">
    <Window name="Mixer" visible="0" x-off="-1" y-off="-1" x-size="-1" y-size="-1" tabbed="1"/>
    <PluginOrder/>
  </Mixer>
  <Preferences>
    <Window name="Preferences" visible="0" x-off="-1" y-off="-1" x-size="-1" y-size="-1" tabbed="1"/>
  </Preferences>
  <Meterbridge show-meterbridge="0">
    <geometry x-size="600" y-size="400" x-pos="1" y-pos="1"/>
  </Meterbridge>
</instant>

This one is bad. Ardour will not start successfully with this setting:
<?xml version="1.0" encoding="UTF-8"?>
<instant>
  <Main x="223" y="48" w="3512" h="2030" current-tab="editor"/>
  <Editor id="39" edit-horizontal-pane-pos="0.99072897434234619" notebook-shrunk="1" edit-vertical-pane-pos="0.89999997615814209" zoom-focus="ZoomFocusPlayhead" zoom="2048" snap-to="SnapToBeat" snap-mode="SnapOff" internal-snap-to="SnapToBeat" internal-snap-mode="SnapOff" pre-internal-snap-to="SnapToBeat" pre-internal-snap-mode="SnapOff" edit-point="EditAtMouse" visible-track-count="-1" playhead="1" left-frame="0" y-origin="0" show-measures="1" maximised="0" follow-playhead="1" stationary-playhead="0" region-list-sort-type="ByEndInFile" mouse-mode="MouseObject" join-object-range="0" show-editor-mixer="0" show-editor-list="0" editor-list-page="0" show-marker-lines="0" nudge-clock-value="0">
    <Window name="Editor" visible="0" x-off="-1" y-off="-1" x-size="-1" y-size="-1" tabbed="1"/>
    <Buttons>
      <Press/>
      <Release/>
    </Buttons>
    <Selection/>
    <RegionList sort-type="ByEndInFile" sort-ascending="1" show-all="0" show-automatic-regions="1"/>
    <ActionScript lua="Lua 5.3">c2NyaXB0cyA9IHt9IA==</ActionScript>
    <ActionHooks/>
    <EditorLocations clock-mode="Frames"/>
  </Editor>
  <Mixer mixer-rhs-pane1-pos="0.60000002384185791" mixer-rhs-pane2-pos="0.69999998807907104" mixer-list-hpane-pos="0.20000000298023224" mixer-inner-pane-pos="0.80000001192092896" narrow-strips="0" show-mixer="0" show-mixer-list="1" maximised="0">
    <Window name="Mixer" visible="0" x-off="-1" y-off="-1" x-size="-1" y-size="-1" tabbed="1"/>
    <PluginOrder/>
  </Mixer>
  <Preferences>
    <Window name="Preferences" visible="0" x-off="-1" y-off="-1" x-size="-1" y-size="-1" tabbed="1"/>
  </Preferences>
  <Meterbridge show-meterbridge="0">
    <geometry x-size="600" y-size="400" x-pos="1" y-pos="1"/>
  </Meterbridge>
</instant>