yep with you on the skirted versus lollipop piston.......they're not made like that by accident are they ?
and you get better control over spring wobble
full skirted ally at 21mm will be at a usable weight or even too light if you try . reckon 120g quite possible.
i'll have to re visit mine, it got sidelined when i couldn't achieve a long enough cocking stroke with a std mk2 lever ....just a matter of relieving a little meat