I have been learning a bit about tuning, and have found the posts on SCR very interesting. I have sleeved a couple of transfer ports down with brass tubing in the past, as well as drilled some out, and now see what the science is behind it.

I have searched, and haven't found discussions specifically on piston weight. I know that my Mercury S will have to be lightened, and perhaps my 26mm HW77. I want to experiment on some less costly stuff first; a Baikal 512M, and an older HW30. The Baikal has a very heavy solid guide that I haven't weighed yet, and surprisingly the Macarri kitted HW30 wants to make the Beeman peep sight move around.

I would guess that there is perhaps a general weight range for power levels maybe? Perhaps the weight is more related to spring wire size?
I have read that the later HW77 piston is heavier than the first, so I would guess that a 6, or 8fpe gun would be lighter yet. Are there any general starting points, or directions to go from? It is all very fascinating.