Eindecker:
The Great Planes "Large Engine Isolation Mount" is a 5 1/4" by 4 3/4" chunk of 1/4" ply with rubber mounts at the corners. exactly what you had suggested.
Maybe,i could isolate the engine,by placing some rubber material,under the engine lugs,or under ply plate,before screwing down...
he FRP mount is fastened to the ply plate, and the ply plate is then attached to the firewall through its soft mounts. And its price is a small fraction of Du-Bro's.
Vibration, at its worst, will shake the airplane apart, strip servo gears. greatly increase battery drain, flex all the wires and break them, just about any problem that could arise from shaking. It is to be avoided a much as possible.
Bill.