I agree this would be a good subject to get the more knowledgable talking about.

I lightened my 25mm 77 piston which worked well in conjunction with expanding the TP.
As I understand it a lighter piston reduces inertia and accelerates faster, but if the escape route for the air is too restricted the lack of weight results in piston bounce. That in turn increases felt recoil.

I look forward to some replies from people who aren't just guessing!