I successfully added some filler to beef-up the arms. Here's how:
1) remove head, cape, hands, shoulder/chest armors
2) slip inner robe sleeves down each shoulder, pass bent arms through holes, pull top of robe down a bit
3) on the back, unfasten small plastic buckle of chest respirator box's harness straps
(you squeeze it in the middle to release)
4) slip harness straps down over both shoulders, passing both arms through, to allow free arm movement
5) unfasten velcro down center rear of body suit
(now you have access to the upper arms of the suit through the neck opening)
6) using the tip of the light saber blade, (at least it's good for something)
stuff small folded pieces of toilet paper into each bicep area
7) mold them into form by hand, add more if needed
8) suit up.
DONE. Well, almost; I'll be inserting a bit of stuffing through the wrist holes,
to add some muscle thickness to the upper forearms.
I just did mine, and the arms look much better.
Of course you can use some other filler material, like synthetic cotton stuffing...
but I used toilet paper, just in case Vader has to use the little sith's room.
