AOTP Studio Series Soundwave Broken Shoulder Fix *WIP*

I created this model on measurements alone (for someone else) without being able to fit the piece myself. I don't know how it fits with the figure; fair warning.

Cover picture is meant to show what I'm trying to fix. It's not my photo, otherwise I'd be confirming the design.

As this is a project I took on a whim to help someone else, I'd be very appreciative if anyone could help me confirm my accuracy in the comments. I know the mushroom peg fits the arm just fine, it's just a matter of the dowel pin swivel portion and the rectangular peg fitment. Thanks.