Fossil- I believe that the OS 70 is about four onces heavier than the Saito 72 and the Saito 72 is about two onces heavier than the Saito 56. I used standard size servos, JR 649S pcm receiver, and a one thousand milliamp nicad pack. Yes, you do have to cut away quite a bit of the dummy radial engine because the 72 is longer than the smaller engines. Constructing the dummy radial and making your engine blend to it and the fiberglass cowl is by far the hardest part of assembling this ARF. But even though I had to cut more out of the radial and the cowl, it was well worth it. The performance with that 72 is phenomenal. We fly off of a grass sod farm and if you land a little hot, this plane does have a tendency to ground loop and flip over. But once you are aware of this, a pilot with normal skills can avoid it by controlling his touchdown speed. I have never flown it off of a hard surface, so I don't know if that would help or not. As mine is setup, it floats right in for landings and does not have a tendency to stall. I substituted aircraft type lock-nuts and socket head bolts for the wing struts and ca-bane.

This ARF was one of the highest quality ARFs I have seen. The only thing that was misleading was it claimed it came with a finished and painted fiberglass cowl so I thought all the assembly and painting of the cowl and dummy radial were done. Wrong.

Other than the amount of time it takes to assemble and paint the dummy radial, Kyosho has a winner with this one.