I've wanted to make this figure for a long time, but it was too difficult to put these details on a 3 inch Jazwares figure, and the 10 inch one is WAY to rare and expensive to customize, so the 4 inch Jakks Pacific figure was perfect for this. I made some basic models in tinkercad and printed out new shin and forearm armor, and extended the length of the legs and arms a tiny bit to accommodate them. Details like the shoulder pads and head spines are made from craft foam, the trenchcoat cape thing is made from a scrap of black denim, and other details like the toes and knee pads are made with apoxie sculpt. I don't like how the spines aren't fully accurate to the game model, but the only way I'd be able to pull it off accurately is to 3D print the entire head and that would be too big to fit in my printer, plus the design would clip into the shoulders and make it so the head wouldn't be able to move anyway. All of Metal Sonic's original articulation is preserved this way.

Edit: I found a way to print a more game accurate model of his head made by Nibroc-Rock, so now it looks more accurate to his real appearance, but I was totally right about how it kills all neck articulation, the lower spines are right up against the shoulders AND the back of the jet, so it doesn't move at all anymore.