Hi thanks much for the adviceYou're right, 24g is way too low.
I have 28g Dr. Pulley sliders/pieces in my C600, with about 5k miles on them. I've found they help with acceleration off the line, but don't really do much to the higher end of the RPM band (it didn't need any help when it was stock). Mileage took a small hit, but I've got to imagine in your case, mileage would improve with the move from 24g to 28g.