It sounds like you might want to mount it on the rear of the trailer, which has some potential for problems. First, the frame is often not very strong back there, and second, adding a lot of weight at the back of a trailer can screw up the weight distribution. How about mounting it in the bed of the truck?
Hey Butcher 61, welcome to the forum. At least 18/20% of the weight of a 5th Wheel must be on the front King Pin. If you add too much weight to the rear of the trailer, you may interfere with the manufactures design balance and cause your 5th Wheel to have handling issues.
Well I just bought a new Honda EU3000is Generator. The weight is only 135 lbs. dry so I don't think ( but don't really know either ) if that will be too much weight either. I saw an enclosure on the back of a newer Silverback that was made with aluminum diamond plate that was really sweet. It had vents for the exhaust etc. and is what I am looking for. Any information is appreciated greatly.
The Honda is what I had. I mounted it in my truck bed in front of the hitch. With a custom cover from a company which appears to not be around any more, I had a hatch over it for the exhaust to exit when running, and closed for security and weather protection when not running. I was planning to wire in a cable out the front, to a transfer switch, but never got around to it before getting rid of the trailer.
135 pounds may be 'not much', but diamond plate has some weight. And keep in mind that this weight is on the end of a 'lever' running from the generator to the hitch, with the axel(s) as fulcrum. Torque on the often minimal frame in that area, and a computable removal of weight from the king pin, need to be considered.