If your racing indoor foam I like the 6deg. If your racing indoor rubber I like 4deg. I also like 4deg on asphalt. What I do to get those degs. is to use the hub Carrier with the next lowest deg. and shim the front hinge block 1mm higher. This will add a little pro-dive, which will give you some off-power and mid-corner steering, at the same time advancing the caster near the desired amount of caster.