Hey mattdorris I think you might be disappointed if you swap out your Wall Street killer onto a TrueType narrow shoulder or knock off equivalent. The suit is tailored to fit the slightly more narrow build of the ZCWO body.
I have two suggestions :
1) buy an agent coulson body, it's sort of like a narrow shoulder but with narrower shoulders and pecs and less torso length. This body looks great in WSK but it's not cheap.
2) if it's the ankles giving you problems there's a couple easy fixes:
A) try simply swapping them with some hot toys pegs sometimes they vary in thickness and could give you a tighter grip
B) some blue tack between the ball and hole can work wonders
C) you could build up layers of gorilla glue on the ball part of the peg, apply and dry with a hair dryer and repeat. Nail polish hardener has the same effect, it technically makes rhe ball thicker so they fit more snug in the hole