This is what I have in my Evo. Cell-phone sized pieces of interlocking foam flooring, wrapped in Gorilla tape as well as low-friction tape and velcroed to the bucket where the widest part of my hips is.
Works very well, improves stability and doesn't affect rotation. As is, this bucket is too loose for me.
As far as bum pads go, I never liked them. It improves my posture but decreases stability and starts hurting me after a while. I can spend forever in a naked bucket of all 3 skis I have owned.
Have the exact same pads in my SES but set more forward. That bucket is tighter so I can't used them on sides like that, but it works to the same effect in both boats.