Big Jim, you are probably a pretty big guy, but the world is full of nuts these days, and a lot of "small" people feel like a weapon of some sort is the big 'equalizer' in a dispute like this. So watch your back.
Don't give him any further reason to get embittered against you, such as posting his name publicly, etc. That could really aggravate this already (apparently) unreasonable person. As far as I can tell just from reading this thread, you appear to have handled yourself like gentleman so far.
Maybe, to close your dealings with this guy, after sending him HIS modified limbs and holding him accountable, you could offer him a discount on a future purchase (not likely), sell him something at cost, or include a 'peace offering' in the package you're going to send him. That could be a way of holding a firm line with the limbs he re-worked, but also placate his anger and re-affirm to him that you are a gentleman and are not just being spiteful towards him.