Multiple Header Templates

I created a custom template that auto-sizes to fit the content - it works fine, but I only want to use it as a header template when the column header is not an html element (one column has a 'select all' style checkbox in its header).

The problem is that when I can set the overall header template, but not for each column individually like I can for the column templates.

My thoughts so far: it looks like I might need to derive from List or Row and implement some custom set/get methods, then replace the top template with the new subclass.

Could you post the template/related code?