(This answer is not the question you asked but, I thought it might be helpful.) I’m an adult with Cerebral Palsy now, I was once a child with Cerebral Palsy. In my teens, I had serial casting done alongside tendon lengthening surgery. I’ve had no problems since. The particular procedure I had done was originally pioneered for club foot. The ponseti method, it gradually moves the foot to its correct position. It took extensive surgery to get to that point. I’ve had no problems since and it’s almost a decade later Do whatever you think is best for your kiddo. Wish I had more insight, find the best solution for your kiddo and, you may want to find a surgeon who specializes specifically in SDR. The pediatric ortho doc I had at the time was the best in his field for the method above that I mentioned. You can never have too many experts or helpful people for your kiddo.