Remove button from Ribbon in a specific toolbar

Hi,

I have created a custom list using feature. the list contains 7 content types inheriting from another custom content type. I have set the toolbar type for different views to "None".

I want to remove the attach file option from Actions group in Ribbon. I tried the solution given in http://sharepoint.stackexchange.com/questions/32606/remove-button-from-ribbon-in-a-specific-toolbar

by specifying custom action with

 the Registration type "ContentType" and registration Id "Content Type Id" for all the content types.

<CustomAction
Id="RemoveUploadButton"
Location="CommandUI.Ribbon"
RegistrationType="ContentType"
RegistrationId="{firstcontenttypeid}"><CommandUIExtension><CommandUIDefinitions><CommandUIDefinition
        Location="Ribbon.ListItem.Actions" /></CommandUIDefinitions></CommandUIExtension></CustomAction><CustomAction
Id="RemoveUploadButton"
Location="CommandUI.Ribbon"
RegistrationType="ContentType"
RegistrationId="{secondcontenttypeid}"><CommandUIExtension><CommandUIDefinitions><CommandUIDefinition
        Location="Ribbon.ListItem.Actions" /></CommandUIDefinitions></CommandUIExtension></CustomAction>

but still the attach file option is appearing in ribbon under item tab. When I set the toolbar type to "Standard" attach file option disappear.

Please help. TIA

-Harry