I've done a quite similar setup with RE11 265/35 fronts but with 285/35 rears last year. I'm on the same 20/25 combo as you're running and from what i can recall, the fronts were cambered at -1.6x and -1.8x at the rears. I've seen some using 305 on the rears, but you're gonna have to camber the rears though.
Edit :
If you want to see my 285 rear rays setups, just check my journal
