I freshened up my motor this winter and bought 8 new pistons. I also went from a set of hand ported 360-1's to a set of 245cc CNC 360-1's which have a 2.15 intake valve instead of a 2.10 so the only changes I had them make in the pistons was to make them for a 4.045 bore instead of a 4.040 bore and to cut the valve relief for the bigger 2.15 intake valve. The pistons are Ross and they also made my last set. I also had them make the pistons the same weight as my old ones so I didn't have to re-balance my rotating assembly. After getting the new pistons and assembling my motor I had piston to valve clearance problems. After calling Ross they realized they cut the valve reliefs too small and I had to pull the motor back apart and send them the pistons back so they could fly cut the reliefs the right size. Now the pistons are 9 grams lighter than my old ones. They are telling me its no problem and I dont need to re-balance my motor. Is this true? Is 9-10 grams not too light? They are telling me its not a problem for the pistons to be lighter. I turn this motor over 7500 rpm's. What should I do?