high frequency dampers -good idea
there is a lot of banter about mounts which allow the engine to flail around --as we once did with our 1.4 four cycle glo engines
The only setup I ever found which worked -- was to mount the engine such that it was free to rotate ONLY on it's crankshaft centerline-- damped in movement by some means - I used an adjustable natural rubber snubber - this eliminated the tremendous thump at low rpms BUT any external exhaust setup either restricted the movement -or got broken.
On our large engines --letting them shake about is a distaster.