Sorry, I wasn't too clear. The 72 is on a totally different plane. I mentioned it because it's my only 4 stroke experience, and it's not all that great. I have a tach, but little idea what to shoot for. I tried to get it to the peak rpm, and then back off a few hundred rpm. I guess I just need to give it time to start to seem right. I expected 9500 to 10000 rpm and got more like 8600 to 8800. For the Giles, the only engines in the heap are the 91FX and the Saito 100. I can get the 91 with a Jett muffler for $265 and I can get a Saito 100 for $260. Both are new engines. I'd expect 11000+ rpm (based on the Jett engineering numbers) with a 14x6 on the 91. I don't see any reason to believe the Saito 100 would break 9800 (based on Horizon's numbers). I believe the 91FX will do about 10000 (maybe 9800) on a 15x6. The Saito looks capable of barely 9000. Reliability and performance are the only factors with a $5 price difference.