Not certan, but have you thought of these:

- Why hot use your main template as the YABB template? Just use your main template and make the mods necessary to turn it into a YABB template. You'll want to add a lnk to get back to your main pages, but this should work

- I think someone else mentioned it, but if your template uses frames, you can modify the YABB template and then the YABB output should be OK in the frame.

- Can you use SSI exec to get YABB invoked as part of the page? Again, might need to change the YABB template to get rid of it headers.

- Try the YABB forums. Those folks are YABB experts and have probably already faced this issue,