generator on rear bumper cargo rack

I mounted a Champion open frame 3500 on the back of my Pioneer 18' and did feel the generator when running, but it was not enough to bother me, but I usually run the generator for short periods only; DW hair dryer, microwave leftovers, A/C for dog during food stops, etc. For that setup, I had stringers welded to the frame and used the bumper as a balance point for the platform. I cut the bottom out of a metal truck box with a locking lid, and bolted the box over the genny from the inside with the gen sitting on a section of truck bed mat. I then mounted drop down hinged doors covering ventilation holes with computer fans and ran the exhaust through the wall. I wired the genny to the breaker box and used a breaker to switch between shore or gen power. I could close the lid to the box and it was pretty quiet. 6 years and close to 13k towing miles with no problems. I had no rear window and never had an issue with fumes.
I now have the Stromberg tongue mount with a Champion 3100 invertor over the propane tanks on my current trailer. I have it bolted to the carrier and have been to campgrounds notorious for thefts (Emma Wood in Ventura for example) and have had no problems...but its yellow so no one wants it anyway. I'm still gathering parts to wire in with the transfer switch, so for now I plug in when needed. No front window on this trailer so no fumes in this case either.
Either setup worked for me with no bad effects on tongue weight.