Dave took Xrays to the surgeon yesterday. He said Dave is progressing beautifully. He does want him to not jar or stress the fusion for another 6 months, when he will have Xrays again. He also said an overzealous PT therapist could cause damage, so that is why he doesn't want him to have it.
From this experience, it seems that a person may have a better chance at fusion using this very conservative approach. It was a pain wearing the collar and not driving for 3 months. Also, continuing to have some activity restrictions. But---it makes sense to give the fusion every chance to take. Just my opinion.