I never lightened the LGV piston I fitted in my .22" TX, I just fitted a HW seal and that was about all I had to do to get an easy 12ftlbs from the shorter stroke.
I fitted the HW breech seal because after fitting the piston the velocity was a little bit inconsistent --- after fitting the new breech seal all was good.
http://www.airgunbbs.com/showthread....7-Operation-TX
All the best Mick