Hide Ribbon Buttons on Form Library

I'm trying to hide some buttons on a Form Library in SharePoint. I put together a feature with the following Elements.xml contents, which hides the required buttons for Document Libraries, but not my Form Library. I'm guessing the Location parameter is different for Form Libraries, but can't find anything about that in the documentation.

The Elements.xml is;

<?xml version="1.0" encoding="utf-8"?>
<Elements xmlns="http://schemas.microsoft.com/sharepoint/">
  <CustomAction
    Id="RemoveRibbonButton"
    Location="CommandUI.Ribbon"
    RegistrationId="101" 
    RegistrationType="List">
    <CommandUIExtension>
      <CommandUIDefinitions>
        <CommandUIDefinition Location="Ribbon.Library.Actions.OpenWithExplorer" />
        <CommandUIDefinition Location="Ribbon.Library.Actions.ExportToSpreadsheet" />
        <CommandUIDefinition Location="Ribbon.Library.Actions.OpenWithAccess" />
        <CommandUIDefinition Location="Ribbon.Library.Share.ViewRSSFeed" />
        <CommandUIDefinition Location="Ribbon.Library.Share.AlertMe" />
        <CommandUIDefinition Location="Ribbon.Library.Share.EmailLibraryLink" />
      </CommandUIDefinitions>
    </CommandUIExtension>
  </CustomAction>
  
</Elements>

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I see nothing in the documentation here for Form Libraries specifically;

http://msdn.microsoft.com/en-us/library/ee537543(v=office.14).aspx

Puzzlingly the above xml hides just one item in the Form Library ribbon, the Open With Explorer, but ignores the rest.

As I say the above works, but for Document Libraries, not Form libraries. What do I need to tweak?