PMK
You may want to put some teflon tape on outside rear edges where it's rubbing. Try to preserve a ride height of 4-5mm. I've noticed on carpet that I was at ride height of 3 mm but my chassis was very black. I found out the springs on the shocks were too loose and tightened it. After that, the chassis never rubbed. You want to be sure you tighten the spring a bit so the chassis wont flex too much to rub on the tarmac.