I haven't tried the lowering blocks from sinister industries but i have tried lowering blocks and imho they changed my ride quality and if you lowered it more than one inch with the block i developed a rub however this is on my road glide custom that is already 1 inch shorter than the ultra. I decided to send my shocks to bitchinbaggers to have them modified to achieve the look i was after and prevent rubbing. They can modify your shock for the length you want from 12 inch eye to eye to 10.25 inches without a rub however the lower you go the less travel and more harsh of a ride. Check out there website form more info, he will modify the shock for your weight and type of riding. Mailed my shocks this wk, will provide an update when they return.