I think you tried a little too hard to keep Prime's head the same. The proportions for Prime's Gen-1 Transformer head and a Pony's head just isn't that close a match. Could you please do another one without having the mouth plate up on the top of the nose and possibly having the top of the helmet and "ear" points line up more with what you would find in a Pony? Its so close but just didn't go Pony enough on the head.
next time you've got a transformer robot up for bid I HAVE to know. My husband is the biggest transformers geek, and I've infected all his displays with my ponies. lol. I think getting him something like this would be a perfect peace offering! Your stuff is SO amazing.