Wow Jim, that's a great little setup. Apart from the obvious thought of foam tape around the edge to help with leaks, I can't think of anything I'd want to modify. I think it's mostly a matter of getting it dialed in. Are you blessed with a set of garments that are similarly sized or do you have a number of sizes of shoulder molds to use? I look forward to seeing your finished use of the Vivak shoulders and how you support them.

Good luck!
Jamie