I found the HW80 to be a bit of an enigma
At 17 to 18fpe they're sweet and smooth; at 12fpe they're "tolerable" but unpleasant. At 10.5fpe they become sweet and smooth again, and a genuine pleasure to use. With the lighter, 7.9g pellets, I was getting the same muzzle velocity as with 8.4g pellets at the higher power, so the trajectory and POI was exactly the same.
Have fun with your tinkering
Paul.