I fly the MVVS 49/Midwest Aerosport and the Webra 50 Speed/Sig Kougar. I use a 11x6 prop and 10% Cool Power in both. The MVVS 49 will approach 13,800 rpm (14,000 with a 10x7) and the Webra is a few hundred less. My MVVS 49 runs rich at mid throttle however both always run wire to wire. Both are very reliable and very noisey. The MVVS 49 came with a tuned muffler system and the Webra came with a baffle-less muffler. The MVVS is a very ugly motor with acheesey looking muffler system but it runs. Both ran superb right out of the box. I don't recall going through a break-in procedure for either. The MVVS 49 was only $99 from Morris and the Webra 50 Speed was over $140 from Nat'l. Hobby in Ga. I also got the Webra 40 Speed. I received 2 head shims with my MVVS 49 and others in our club didn't receive any with thew same engine. I never installed them. The Webra 50 is ABN and the MVVS 49 is ABC. I have a slight preference for ABN but my MVVS is very good ABC engine.