How to create an Item Template Category using VSIX deployment when referencing an Item Template project?

I know that you can have your custom Item Templates appear in custom categories in the "Add new file...." dialog by creating your Item Template zip file, and placing it in "C:\Users\[UserName]\Documents\Visual Studio 2010\Templates\ItemTemplates".  So for example, if I wanted all of my company's custom item templates to show up in an "iQmetrix" category, I would place the item template zip file in "C:\Users\[UserName]\Documents\Visual Studio 2010\Templates\ItemTemplates\iQmetrix".  Then in the "Add new file..." dialog my template would show up under Visual C# -> iQmetrix, instead of directly under Visual C#.

The problem with this is that it requires the user to manually copy/paste the item template zip file into the correct location.  So instead I want to have a VSIX package install our custom item templates automatically.  So I created a new solution that has a VSIX project and a few Item Template projects, so when I build the solution it packages the item template projects up into the VSIX file.  When using this method, it doesn't install the item templates to "C:\Users\[UserName]\Documents\Visual Studio 2010\Templates\ItemTemplates".  When I do "Add Content" in the VSIX manifest and reference the item template project directly, the item templates are always just under their language category (e.g. Visual C#).

Instead of adding a "project" in the VSIX manifest, if I add a "file" (pointing it to the .zip file created by the item template project) then I am allowed to specify the "Add to subfolder (optional)" parameter, and putting "iQmetrix" in that field causes my Item Template to be added to an "iQmetrix" category like I want.  The problem is that the "Add to subfolder (optional)" parameter is disabled when directly referencing a project (rather than a file).  So how can I specify the category to place my item templates in when directly referencing the item template project?

Thanks in advance!