Fractured/sprained left wrist from snowboarding, + re-injured wrist months later from skateboarding = Months playing in a big brace thing. Lame? Yes. Doable? Yes, definatley. Plus, playing solo competitions in a big brace = mad props, yo.

I highly reccomend learning to play on a low stool, with both feet on the ground. And yes, learn to play "over" the bass, instead of gripping with your left hand. Think like you're applying thumb position technique all over the bass; fingers arched, driving those strings into the fingerboard. And think about going, with your bass, to a body worker. He can help you evaluate how all your mechanical systems are working together, and straighten out your body so everything is absorbing stress equally and flowing together, without focusing pressure and stress on any one spot.