Straight (not angled) non central TP (for obvious reasons, as stated)
Non rotating piston as it has a cocking shoe, which slides in a slot in the piston
Also, I note the latch machined in the end of the piston rod is a lot stronger than a TX style "mushroom" rod, possibly to better handle the higher load
PE doesn't have a comp tube, or a tight spot in the cylinder
Trigger is the same as a TX, so a TX piston rod does work

Great guns, just not very sensible.