This pushing off the rubber is very tempting. On a gun, I gained abou 8 - 9 mph (71 mph) more when pushing off the rubber, BUT here's a big BUT, my shoulder took a beating. I went back to not pushing off the rubber and I could only hit 61 mph, but my shoulder felt fine. Pushing off the rubber is something that you hear at little league games all the time, I think this is a big mistake.
I think I will just stick with rotating off the mound for now.