Piston weight difference

I bought 18 SBC LT1 PM rods when we were gathering parts for my kids dirt modified.

The weights vary by 15 grams. These were nearly new rods that came out of marine engines that froze during the winter.

These rods are used by hundreds of guys in their dirt cars... Most engine shops screw em together and simply balance the cranks.. new pistons are pretty close on weight
Anyway that 15 grams doesn't seem to make much difference in these motors running 50 or so laps per week at 6500-7000 rpm.

My son's engine runs smooth and strong.