BTW, we've been remiss in our advice.

We forgot to mention that there are vibration absorbing motor mounts available.

They are very popular with the pattern crowd. That bunch seems to have a large number of fans of engines of a type known for strong vibrations. It was noticed by some of them that they really couldn't keep their airplanes alive just by wrapping the RX in foam. And a couple of guys developed "soft mounts". And then they discovered those mounts seemed to increase the horsepower that was getting to the prop. The mounts were actually putting the power output of the engine into the prop instead of the airframe.

So if you've got an engine that vibrates, it would be to your advantage, in more than one way, to mount it with one of the soft mounts.