Tuning Rws 34 piston seal

I gotta ask... is it the right seal? I've had some rough ones before but never had to pry them on with a screw driver. Usually a bit of heat from a heat gun and it will pop right on. To help break in, size it to the tube. A tight seal takes forever to break in and shoot well.

It's the 28mm seal. I finally got it on and reassembled the 1st Gen Diana 34 that I picked up. I put the seal on the way Vortek described in a video on their website. Piston fit nice with new seal and shot 8.6 gr (weighted) JSB's @834 fps. A little better than it was. Changed breech seal as well. Velocity will probably go up a little.