Cosplay Construction Question

[Jeahanne]

So, I don't know if there's anyone out there who makes a lot of Cosplay and might be able to answer a question for me, but I thought this might be the place to ask. I'm working on the Manduka Operator Suit hoodie/jacket thing for TennoCon, and I've gotten decently far along, but I've run into one odd issue. The sleeves have some structure in the upper arms that's very irregular.

I've bought some Flexfoam, which I plan to use in the hood to help it keep it's shape once I've "quilted" in all of the decorative lines, and I planned to use the same stuff to make this shoulder adornment and the further decoration at the end of the sleeves, but I really don't know the best way to go about using and covering it, if I'm even on the right track. I had planned to make the actual sleeve one piece of fabric, and add this decoration on top to help keep the sleeve itself even and properly fitting. The issue I have is making the foam do what I want, and then covering it in such a way that I don't end up with puckers and badness at the end of it all.

Does anyone know of a good way to get these shapes and cover them well? I've searched the internet for help and come up empty, mostly because I don't know how to search for this problem. If I need to go out and get a different material, I can. I'm just at a bit of a loss. So far I've managed to get everything else looking semi-decent, so I'd hate to fall down and mess the sleeves up terribly. Thanks in advance for any advice! <3