It looks like you did your homework really well. What you've done so far is very good. I'm not sure what you have planned to pad the panels with, and I'm not sure I understand where the stainless will be. Is it going on the bottom layer of foamboard panel and then the top layer is cut out to let it show? If so, that will work just fine, but make the ends round or you will have problems getting the fabric to go under the opening. The contact adhesive will hold the stainless on the bottom panel just fine. You don't need to bevel the panel material if you're padding it, but you could just lightly sand the edges if you're not padding it.
As far as the pull strap goes, it will need to be wrapped over something really strong that can be sewed through, like polypropelyne or nylon strapping, and then it should be sewed down. This will hold it all together, and the stitching will be decorative as well as functional.
No one lives forever, the trick is creating something that will.