You are awesome bro, thanks for your sacrifice. I would take a calf piece and assemble it, then I would cap off the top and bottom and place a pipe like piece inside roughly the same size as my prosthetic. Then I would fill the cavity with foam and make a key that would hold it all in place. That way you can just snap it into place and velcro as usual in back. I would love to see the build thread on this because you would be an inspiration to others. Be careful with your rod/prosthetic I hear they can cost alot of dough.