Heavily changed subtheme, better to create a theme?

Hi,

I've been working on a site based on openpublish for a while. The site is growing and the theme has changed very much, it actually looks nothing like the main openpublish theme. Im currently having an issue with IE7, the oldest browser we're supporting (we're running heavy jquery stuff, for instance) and the browser gets hammered everytime it loads my stylesheets, and the one cached from openublish.

I tried to make a duplicate of the theme (please do not refer to the part where I kill the kittens... yesterday someone told me I was doing a massacre), changed the info file in order to have drupal recognize it as another theme. I then turned it on and selected it as the default but the page-header.tpl and the page-footer.tpl do not load. Is openpublish unable to use another theme?

I guess i will have to have my css overwrite the default openpublish stylesheets for now, so they dont get loaded, i really think i dont need them.

Suggestions are welcomed. Thnx!

PD. I must say i know the benefits of creating a subtheme, but there are of course drawbacks like these when you have a site looking veri different from the original theme.