I have a pair of Honda 2000 inverter generators that I put on my rear bumper when boondocking. I have them locked to LowPro LockDowns.
The real fact is that you definitely feel and hear the vibration and noise when they’re mounted on the bumper. The kids didn’t complain in the bunkhouse, but we’ve never tried running them overnight. Once you get into the living room, it’s not an issue (Sabre 36QBOK).
I’ve considered trying to add some kind of rubber isolation mat between the bumper and the LowPro LockDowns.
I’ve never traveled with them there. Hope that helps a little.