I've got an MVVS .21 on my Combat Gremlin and it is a screamer!! It is as fast or faster than the guys flying similar planes with O.S. FX .25's. So far, it has been very reliable. been in at least three violent mid-airs and I've had to replace the needle valve once as a result. Transition is INSTANT! Like a factory tuned two-stroke dirt bike! I have a NIB MVVS .26 combat wombat that I am going to strap on in the spring. They are made to run on 0% nitro, but you can shim them and run them on up to 15%. My .21 is shimmed and runs great on the nitro, but I ordered some 0% and am going to try that right out of the box with my .26. If it doesn't like that, I will try the shims and my 15%. Hope you have the same luck that I've had!!

Jeff