A little help with foam Iron Man

Hey guys/gals,
First time posting a thread. Well I'm doing my first project, a Mk7 Iron man armor and I ran into a little problem. Im using 3/8" EVA foam and I already did the biceps and the forearms, and when I tried to connect it using chicago screws, the arm didn't have much mobility. I was thinking on extending the lower circular part in the bottom of the bicep, giving it a little more space for it to move, but I'm open to any suggestions you guys have. Thanks in advance

Thanks for the reply JF, well cutting it when it's already glues will be very hard., I can try i though.