MVVS truly makes a great engine and the .91's rear exhaust option looks as if it could be right at home in the UCD. I've had (2) .49's for fun flys and a .77 for my Diablotin Super FG, all w/ tuned slncrs and these engines can really perform. Crisp transitions. It's the engine I would've chosen if I did'nt already have the S.1.80.