Short stroking a springer is done to reduce its power, without increasing its lock-time (time lapse from trigger releasing piston, to pellet starting to move - or, more strictly speaking, leaving the muzzle). It is harder to shoot a springer well if it has a sluggish piston, compared to one with a short shot cycle.The R7 / HW 30 is already very easy to shoot well. If you short stroke it and take just enough preload out of the spring to maintain its lock-time (or shorten it slightly), the air rifle should be just as easy or a little easier to shoot well.Strictly speaking, you could leave the spring full length. If you think about it, too long a spring results in coil-bind when cocked. Spring room when cocked is unchanged with the long seal. What will have changed is swept volume (down); and spring preload when uncocked. The latter will increase the amount of force on the spring clamp, when installing the spring. The increased preload in the fired state may increase piston slam, due to the reduction in swept volume. Then again, there is less travel distance for the piston to pick up speed. In any event, if installing the long seal causes harshness not previously there, then reducing the spring preload is probably indicated.
I was talking to OC about these when I seen them, as he was making some of his own. These should snap right on the piston. The only change I can think of is when you break open the barrel, it will fall farther before the slack is taken up between the cocking arm and the piston. My HW30 with the Vortek kit at 10m will give my FWB300's a good run for the money,Jason