I'm Ready To Break My Phone!

I need help from anyone who knows FOR SURE the best way to downgrade from 2.2 Beta 1 (current seeded Beta software for Testers) back to the current public release, 2.1 5F136?

The problem is that there was clearly a significant Baseband update while installing 2.2; significant framework changes as well.

I've tried everything that I've been able to downgrade with in the past & nothing.

Does ANYONE know something I don't? Oh yes, this is for an iPhone 3G.