For those who did not fully read page 1 of this discussion here is relevant info.
The National Electric Code has a long section, Article 551, dedicated to Recreational Vehicles and Recreational Vehicle Parks. Here is the specific requirement for RV generators.
Article 551
Recreational vehicles and recreational vehicle parks.
Part III. Other Power Sources
551.30 Generator Installations
(A) Mounting. Generators shall be mounted in such a manner as to be effectively bonded to the recreational vehicle chassis. The connection of the electrical system produced by the generator shall provide an effective ground-fault return path when operational.