Backspacing question - 4.5/6 drop, 17" Torqu Thrust II's

[glock35ipsc]

I was hoping someone had close to the same setup as I am thinking of going with. I'm looking for what backspacing will work for this setup:

Front - 17x8 Torque Thrust II's, 4.5" drop (spindles & 2" springs), stock A-arms

Rear - 17x9.5 Torque Thrust II's, 6" drop (5" springs & 1" blocks)

It seems the rears are only available off-the-shelf in 5" BS (custom available for $$$), but the fronts I have seen 4", 4.5" (Eagle 211's), and 5".

If you are running the TT II's or American Eagle 211's on the front, and they are 8" wide, with a ~4" drop, what backspacing are you using?

Thanks!