When I built my kit I was reading all the info on here about pistons and was determined to drill out a few holes. All I had was a 1.6 bit "thought it was 1.5" so I went ahead and drilled 4 holes in each 10x1.1 piston leaving me w 6x1.1/4x1.6 total hole surface of 13 like the 10x1.3, 35/30 losi was way to light, I ended up racing w 45/35 losi but this week I went to our indoor track and bumped to 60/50 AE "I kno it sounds way heavy" but It felt much better, granted it was on a smooth indoor clay track. It seems soft on the bench but seems to pack up well over jumps and lets the car roll enough in the corners for traction. It may be too heavy for a bumpy track, we'll see. I did order CSI blue v-ports that should be here 2day, 2.8/2.6 swaybars and tires/wheels should be here soon too.