The Mvvs engines have excellent top end and idle very well. However of the six engines in my club none of them transition very well at all. Morris hobbies has been pushing these engines for their hovering and transition qualities which ironically is the one place these engines do not perform well. My 75.00 thundertiger .46 has far better transition and will out hover a MVVS .49 all day long. One member of our club just bought a .77 and tuned pipe for a Ohio Models YAK profile. After screwing with it for two weeks he gave up on it. He offered it to other club members for 100.00 bucks and got no takers. Another member has a .65 that will idle great and really screams at top end, but practically dies on transition. It was sent back to morris hobbies and they supposedly did all kinds off work on it, and it still runs the same. These are great all out racing engines but do not buy one for hovering type fun fly planes.