if you're going to remove metal from the piston I would suggest just carving the metal away from areas that it doesn't need to be. the intake port is a little bitty thing but the piston skirt there is a solid inch and a quarter wider than it needs to be.
on a reed valve bike you can make the intake side of the piston way way way lighter by cutting the intake side skirt almost completely away.
my preferred method of lightening the top end assembly is to drill out the wrist pin or switch to a titanium one. I've had bad luck in the past with commercially available titanium wrist pins (none of them are properly hardened) so I had a machinist buddy make one for me a while back and it's been working well. I don't know if it's because it's properly hardened or because I've been using a bronze bushing instead of a bearing that it's holding up. it's worth investigation to see if a bronze bushing with a commercially available titanium wrist pin will last.
and of course a properly trued crank makes a massive difference. a lot of cranks from the factory are tighter on one side, I've seen as much as 60 thou difference. just chinese manufacturing for you. I simply take the crank and stick it in a vice, then start cranking down on it until the runoff is too small to measure with my equipment. if I go to far, turn it over and pry it apart a bit.