What I did a few years ago... This was my set up;
And my TPC;
Reg was set at 450psi, I used a stock valve spring, and a blue main, with a very consistent 270fps.
I don't like a 3.5oz'r in the verticle position, and I'm not to crazy about a BBA either, so I mainly use 12g's, which for some reason didn't work well with that set up. Mayby GGurl might know why that was. I just never botherd to find out.