Only to a point, Jayjay. You need mass to minimize piston bounce which reduces power. As in most things airgun, there are tons of tradeoffs. You just have to decide what's more important and proceed accordingly. A person could drill holes in an existing piston to lighten it enough, I think. If you go too light, you'll have to put more spring, which makes it harsher, in order to get power. I believe Jim Maccari used to sell tophats of steel which increased preload and added mass to get more power.
If you look at JohnnyPiston's posts, he details the modifications to many nice rifles done in a VERY good way, for shootability and pleasant behavior, as well as more power in some cases. Not a bad role model for this, especially since he seems to find some really nice parts that aren't mainstream.
Have fun experimenting, regardless .
My $0.02.
Bob
