Thanks for the info. I didn't even think of a 3-blade prop. I am going to try that along with the aftermarket muffler. This .25 is about 15 years old, so I believe it has a muffler with no baffling - it is LOUD! I also have a .35 that is a bit older, but still runs great - I haven't run that motor in about 13 years but I recall it being slightly quieter than the .25. I am going with the .25 because I have the notion that the .35 would be too heavy for the plane. I could be wrong though - would the .35 be a better engine for this plane? Would it be queiter do you think?