Stitched elastic strap with Velcro onto arm piece and riveted on outer plastic shroud.
Again I had to notch hood to fit shoulder movement.
Found some handy aluminium washers designed for rivets at hardware store, decent price too.
The second shoulder shroud assembled much easier with rivet washers.
Took a 90° angle plastic piece, cut notches on one side, warmed it with heat gun, curved into place, placed one center rivet, let cool.
Then continued around remainder notches, warmed the last tabs again, finished last rivets and let cool.
Final result turned out perfect.
The Autobot logo on side will look cool, white or red color?
So I completed both sides of shoulder and upper arms and did a test wearing it, my mobility so far is good, and should be good with chest fenders and hood attached.