Thanks for the compliments guys! The last two are indeed from a Hasbro 12" figure, just for fun The helmet itself is a full size, though I'm not too sure which version. In the Ebay-description he said it was Mystery sized, but I'm not sure.
It's indeed a shame he didn't mod everything, but I'm more than happy with how it came out. I'm not too picky about all the details for my first one, just happy to have one