Have you checked the bike's fit? Sounds like things may be off, if you're just riding around town I don't personally feel you should be in so much pain. I had some aches & pains when starting to learn to skid, but nothing like what you describe. Seems like something ain't right with your Pista's fit, because if none of the other bikes are causing these pains then something is different about the Pista. The FG should have nothing (or very little) to do with it IMHO.

Steve