Eindecker:

You have a good idea, I only see one problem.

Engines, when you get that large, have some pretty hard vibrations. Fastened rigidly to the plywood and the beech bearers every bit of that vibration is going straight into the airframe.

If you have the room, you can use a FRP mount with the beams 3/4 to 1 inch wider than the engine needs, and then use your ply plate between the mount and the engine. The fiber reinforced plastic mount is a pretty good vibration isolator. Or you could get a Du-Bro soft mount, the Great Planes "Large Engine Isolation Mount," or any one of several others. The GP mount is just the isolator, you'll have to use a conventional FRP mount with it, unless you get a radial mount adaptor for your engine.

As I said, you had a good idea. And you might not have any vibration problems, anyway.

Bill.