I guess it's safe now to reveal a "secret" since I most likely won't be racing any of yuse.
When choosing pistons from your quart Mason jar full of pistons (You do have at least one jar full of used pistons don't you?) tweak & lock your mike to the size that allows the piston to just slide through with a slight drag. I have the number written inside the lid of my mike box but it's been a while and I've forgotten it now. Anyway, check each & every one in at least 2 places to cull out the ones that aren't ROUND. You'll quickly get a feel for the slight drag on the 1st check, rotate 90 deg & it either flops through or grabs. The good ones feel the same wherever they're checked. Most fellers forget that pistons
must be round to seal properly and many of them are not actually round.
Pick a few ROUND, unscratched pistons, reset the rod & select fit them to twin fluted cylinders that allow the pistons to move up & down freely (dry) with a little drag at TDC and let me know how it goes.
Mix & match them long enough & once in a while you'll get one that's pure magic. Broad needle, great fuel draw, amazing mileage & fast enough to lap your buddies at least once per tank.