About 12 years ago, I had a welder friend engineer and extend the frame and construct a full width shelf on my travel trailer specifically for my Yamaha 3000 generator. It was fine for carrying the generator, but the first time I fired it up, I discovered why it was NOT a good idea. The vibration sent sound waves the entire length of the frame, on both sides. It was loud and annoying and made the whole trailer vibrate. I tried mounting it on vibration dampeners and nothing helped. It ended up back in the bed of the truck and the rack was used for storage.
My advice is don't waste your time or money.