I don't think vibrations or off road driving will affect it, due to the gyroscopic effect... Jarring would try to slow down the spinning, but I don't think it would make any difference in performance. Spinner's tech support was very helpful to me, you could ask them to make sure.
The Spinner IS noisy and does vibrate some.... I can't hear or feel it over the noise of my deuce's idling engine, but you can when you shut the engine off and it slowly spins down to a stop over a minute or so. It's also heavy. It comes with nice rubber vibration dampening mounts, but the instructions warn you not to attach it to sheet metal because it will transmit vibration and noise.
Would a fabbed bracket that bolts to the frame and supports the Spinner in free space in the engine compartment work? The deuce's engine compartment became surprisingly small when I offered up the spinner.... I held it in the space where it needed to go, took measurements, and then welded up a bracket, so it is bolted to the frame but sits about 10" above it.
Jon