I can't say about the Shock Trooper model, but I did this with the WGF Samurai and Ashigaru line with Cadian parts. The scale should be roughly the same.
The WGF models are true-scale 28mm while
GW stuff is heroic scale. The dimensions are close, but barely. I had to us
GS on EVERY model to bulk up the shoulder area enough to make the arms fit and look better.
WIP:
Final: