Built two 22mm skirtless piston tunes this week , in an attempt to utilise the standard TX mk3 spring. I have them at 87mm & 90 mm stroke . Making the power ok,and easy to cock, though after a couple of hundred shots I am finding the spring ends (piston end) are developing a set in them, this then seems to make the piston bind and the power gets inconsistant. Shot back to back with a similar full skirted set up, they seem to move more , I am thinking its down to the extra spring room available in a full piston. I used some second hand springs for these, so have new ones on the way to test further .