This may not be the case, but have you considered that the back problems could be from emphasizing back mobility over hip mobility? I have wondered about this in the case of gymnasts, as there is typically a good bit of both involved in the sport, but how are you with Coach's hip circles? You know, the 10 to the front, 10 to side, and 10 circular? Can you do them without your pelvis moving out of a neutral position? Can you hold your knee well above parallel with the ground with a flat back against the wall for 15+ seconds?
Just trying to troubleshoot a little, I don't know the first thing about your back injury's origin or even what it is. I've been reading a bit, and apparently a lot of back problems in athletes seem to be coming from using the back for mobility instead of the hips, especially when performing rotational movements.
What is the back injury, anyhow?