Thanks all for your comments. Here's an update on the Han & Luke in Stormtrooper Disguise.
I wanted to use the Rogue One Single carded Stormtrooper head for these, as it's such a good helmet. I initially wanted to do it as a removable helmet, but it's too small to drill out and fit over a reasonable sized head. So I just drilled it to fit as an alternate head-helmet. As it was going to be a headswap anyway I decided to try different heads and I think the TLC Han Death Star and TBS Luke Yavin work well, both fit well without modifying too.
I wanted Luke to be 'a little short…', so I hollowed out the recess in the upper torso a bit more to make it fit lower. It's not much but I think it improves the Luke Stormtrooper look, especially with the helmet head on, which I also drilled a little deeper than the one for Han.
Trash Compactor Luke with alternate 'wet look' head modified from a TAC Concept Luke.