Turning back to my Sigma Six Marvel line, I took a Sigma Strike Duke and added the face mask from a different Duke (did not have the helmet from the first Duke, would have been easier.) Over the course of a few days, I kept adding Green Stuff to little sections around the mask, taking the mask off after each time it dried. Once it was finally enclosed, I finished the rest of the head and added the chest piece/arc reactor. Gave it a base coat of Model Masters red spray and continued with multiple hand painted coats of Tamiya and MM to complete. The mask is completely removable though it does not "seal" as well as I would like. Guess no space travel or underwater work for Mr. Stark.