Yep full power with 8.4 jsb
I can't remember if there was a great deal of pre load 20mm ish!
It completely depends on how you set piston up, how much shoulder at nose you use etc..
I run a 22 seal and not o rings also..

Nick g uses o rings and his conversions do fire beautifully,

If you can get to a bash meet shoot his rifles and see for your selve,
Tony s conversions are there to.
Wonky donkey etc
Shot cycle is a personal thing, and to ones it's smooth like snapping glass, to the nxt at it's fast, harsh..
You really need to shoot a few different conversions to see which if any suit ..
To be honest I really like my 25mm ally piston one the best, yep sure it has more sight movement, bit more recoil, but accuracy is spot on..