Well chevyart, sounds like installing a 4.5 PV would be a complete & total waste of time if a 3.5 didnt work.
Now dont get me wrong, I'm all for baby steps when it comes to tuning but sometimes you can get hung up on too many small changes and get frustrated (you sound frustrated) .
Bite the bullet, make a profound change, you can always go back, if that 6.5 was working in the other carb - I'm gonna go out on a limb and say it will work in the new one.
So stick that 6.5 in there or better yet plug the hole(s) jet up accordingly (not 8 either, more like 5-6) and be done with it.
Cp