Ok, so, there are a couple of issues at play with the Stealth Strike Suit, and they cause separate problems.
A) The fatsuit which is meant to pad out his torso actually makes his chest look flat and restricts movement of the TrueType's rib joint
B) The rubber shirt and elastic strap work to pull the shoulders together too tightly, restricting movement and giving him that "shrugged" look.
Here's a sketch of the TT body, and the way the shoulders work:
View attachment 189506
The shoulder ball joints are attached to another block inside the chest that allows the entire arm/shoulder to move up and down. With the rubber shirt's elastic strap across the back, the shoulders are pulled closely together, and that means they're pulled up.
If you snip the elastic strap, and slice the collar in the front and back just a little bit, now the shoulders have the freedom to drop down, giving Cap a broader shoulder, more of a neck, and a larger range of movement.
View attachment 189507
You can handle the fatsuit in a number of ways... you can leave it, if you don't care about the rib joint movement/flat chest look. You can slice off
just the part below the rib joint, leaving padding around the pecs but none around the stomach, or you can do what I did and remove it entirely.
The True Type
is muscular. The arms inside the Strike Suit are snug and bulky and look good. But the Strike Suit was tailored to fit over the fatsuit, and so if you remove the fatsuit, the overlying strike suit will not fit the body snugly, thus showing off its musculature.
So I cut the heads off two plastic spoons, and shoved them under the tight rubber shirt, thin ends pointed up towards his clavicle/shoulders.
View attachment 189508
This gives his chest a nice solid and natural protrusion, without limiting the articulation of the rest of the TT body. You could also accomplish this with fabric or clay, or whatever. Someone suggested spoons, and I tried it and thought the curvature of the spoons mimicked the shape of the pecs really well under the suit.
Does that help?