RE: Windsurfing after a back injury
I've had some issues that affected my back, but it's important to note that they weren't the result of windsurfing. The question you need to ask yourself is whether you can really windsurf. If windsurfing didn't cause the injury, your chances are better that you might be able to windsurf earlier than anticipated.
Overall, I wouldn't recommending going against any direction from your professional medical advise, but sooner or later you need to decide if you can handle the stress of windsurfing. it's purely a personal decision, but one that ultimately needs to be handled, especially if windsurfing might be in your future. Believe me, age can remind you that it's there. Otherwise, we would be still competing with KP at the limits. I only wish!
As the second poster stressed, you must ultimately concentrate on your path to strength to help you decide.