You read my mind. I've got a 4mm lower stroke piston sat in front of me waiting to go The only thing stopping me is that the length of stroke does have a slight impact on my aim points, even if the muzzle energy is the same. I won't pretend to understand why it happens, but it does.
If tomorrow's test doesn't work, this piston will be going into the gun until the new seal arrives.
The shoot tomorrow doesn't matter too much, as you can drop a couple of bad scores over the course of the series. But Sunday there are some major bragging rights up for grabs so I won't take any risks for that one.