Nick Ziroil used a .50, it is a 60 size and weight plane, I just happen to have a nice SK .80 on hand I am using. I think it is over kill on power but I was thinking of the added weight to help get the CG without adding any lead. I also have a Bison pitts muffler for it. Plane #2 is going to be electric but the motor hasn't been chosen yet. Not mine, I'm just building the plane and not worrying about the set up or problems my friend may have with it. I am building in the mount and hatch for the battery and putting it forward. The plane does come out tail heavy as Nick built it. One trick is to lengthen the nose a couple inches. I'm almost ready to start mounting the floats. When that is done I can mount the engine and set the plane on the CG machine to see what is needed. Sometimes next week I should know.