Haven't seen the RSX mold up close, but I'll have to have a close look at some pics. Almost bought a BT prowl tonight, but the prices at Silver Snail have gotten kind of Steep.
Also looks like the cap at the back of the seat doesn't hold the ankle ball-joint on, it just keeps it from pivoting too much. You can actually make Grim a half inch taller, if you don't mind him looking like he's wearing floods.
(Think Charlie from Street fighter Alpha)
I have a few other things I should get back to work on first. I'll mess around with this some more later and post any interesting results.