We also considered installing an OS 120 in there, but the 120 is alot smaller, and would have needed a different motor mount, move the engine way forward to clear the front of the cowl. Too much trouble... Also, the muffler wouldnt fit the OS either. This thing is 1/3 bigger than the OS 120. I dont think the 120 would have the nads to pull that big plane, but I may be wrong about that, it just looked so tiny by comparission. As I have seen here and in the past, the 2 strokes slobber oil everywghere and all over the planes too, so thats no good either. The ST was terrible that way bigtime ! My Saito's run as clean as my Chevy, and thats a good thing.