You mean you want to put it in the compartment where your RV type Onan is now. Heat will likely be an issue as the HF generator is surely not designed for operation in an enclosed compartment. The RV generators have fan and air passages designed specifically to cool in the compartment.
It's possible that the movement of the RV will be enough to slosh the fuel around in the carb and not let the generator run right. I have a friend who mounted a "regular" portable generator at the back of his converted bus. It ran find stationary but wouldn't run while in motion. Could have been fuel slosh, could have been the vacuum created at the back of the bus. Either way, it wouldn't run.
What's the problem with the Onan? I'd fix it. If for no other reason than resale value. If I was looking at a used RV with a modified portable generator installed I would assume the owner had modified all kinds of other things and walk away in a hurry.
