I run on carpet with foams, I've been used to having big difference of shore ratings front to rear on my Pro 3, but with my Pro 4 I can run the same shore rating all round the car.
I was told to take all the spacers out of the suspension mounts to lower the roll centre as much as possible, this let the back end come out a little for really tight corners and made it handle really well.
Still running stock suspension mounts, springs, oil, no sway bars, changed the shock positions a little, but that's just about it.