I dug an already converted Ryobi out of the shop because I wanted to see if I could shorten it a bit. The result is a side mounted carb and a prop to firewall distance of 5". The change didn't affect the rpm and with the 1/2" pvc ell on the carb I picked up a couple of hundred rpm. Not shown is a ST 90 muffler with a 1/2" outlet and 360 degreese rotation. The flywheel and cut down coil weigh about 8oz. total. 16/10 prop spins 7440 rpm with an actual quiet muffler. Stock carb. Just wanted to see if it would work.