Another way to do what Simon's suggesting is to just write the form template directly rather than referencing a general-purpose template in your "formtemplate" tag.
The "right" way depends on whether or not the HTML changes you're making are ones you want to use in a bunch of forms (in which case it makes sense to write a new general-purpose template to put in forms/resources) or changes that are specific to that one specific form you're trying to build.
The documentation for this is a bit sketchy ...
