just changing it and riding it as you are now won't comprimise any integrity. If you are doing it to change your riding from XC to something more hardcore then maybe the bike wasn't designed for it. It will slack your head tube and seat tube angles by more than 2 degrees as well as lift your bottom bracket.
It will look almost as relaxed as a dutch commuter bike.
Last edited by KNEEL; 03-04-11 at 09:02 AM.