>>7576712I know it's kind of a late reply but the cup thing just sits between the head and the torso, fit it into the head like the diagram says, and then insert the head, it should stay put. It's not very steady but it does the job. Also I did not have any issues with his cape so you may want to contact GSC in case it counts as a defective.
Excuse the shitty pic, proper camera died so I only have my phone.