Yep, gotta hold and shoot the P7 just a little different than other guns because the recoil is more linear that rotating the muzzle upwards. If you compensate for how other guns move, you'll miss, as you found.
Assuming the piston is in spec, how soft or harsh anything shoots also depends on the ammo. I know from trying out various reloads that both my CCP and P7 dislike the hottest stuff. Increase in recoil until at a certain point, it jumps from slightly more recoil to almost painful, I'm guessing because at that point it's too much for the recoil mitigation system (recoil spring and gas cylinder) and the slide's bottoming out. Almost like going over increasingly large bumps in the car: you feel it but the suspension soaks it up...until it bottoms out.