Just something else to think about. I was mounting another OS 1.20 pumper in an Extra, it was a short term replacement for a YS 1.20. With the GP adjustable mount the engine stuck out too far and the GP mount wouldn't allow the engine to go back any farther, the mount was too thick and the front wheel mount hole was also in the way.I ended up ordering one of the aluminum OS mounts and it made everything fit perfect. The holes were drilled and tapped perfectly too. Take this with a grain of salt. I'm not sure if I was told or read that the four strokes are to at least be mounted in aluminum mounts and not the nylon type because they can torque and flex thus breaking the case of the engine.
Maybe this was just folk lore from the peanut gallery and I over heard it. Just one of those fact or fiction things??
I kit built the Extra I installed the YS 1.40 in and used the Jtec mount. I had the mount in hand and knew what I had to do. I made the fire wall thicker so i could counter sink the mount holes. To get the 2 degrees of right thrust, I have built several of these old CG kits and know what they like, I made a shim that went behind the mount, it too was drilled just for the mount. This way I could dial in any more or less thrust if the plane needed it.
The mount is very impressive but it is more work to mount to the fire wall and lends itself to kit or plans built planes more so then an ARF.
Dang, I'm just full of trivia, or is it just BS??? Perhaps a bit of both???