Update on the Yamaha 3000iSEB ...
We've now got quite a few trips on the "new" 28' Four Winds trailer. We custom made a rear carrier for the Yamaha generator.
http://i124.photobucket.com/albums/p31/westtexashiker/RV/PA270008.jpg
In the pic in the link above you can see the Yamaha on the carrier. This is NOT, I repeat, NOT, just a standard receiver carrier riding in one of those RV rear bumper receivers. We took a receiver carrier and modified it to sit on TOP of the bumper, and (although hard to see in the pic) have angled braces under the carrier that run to the frame. As it sits, it'll hold about 500+ pounds and is super stable. When travelling, the generator sits to the left of the carrier, situating it in the rear center of the trailer. There's enough room for two 5 gal gas cans next to it. When parked, we can unload it and move it away (I've got a 50' 30amp extension cord), but most of the time we just roll it to the far right of the carrier to allow plenty of breathing room for the water heater module. It's so darn quiet! Like folks above have mentioned, we have a security cable that runs through the generator frame and around the RV frame. Heavy duty ratchet-type cargo straps hold the gen and gas cans firmly on the carrier when driving. Not seen in the picture is a nice weather-proof cover I found that fits perfectly over the gen and gas cans (heavy duty patio furniture cover if I remember right...ps..let the gen cool before putting it on!), and gets strapped in place with some bungie cords.
No offense to earlier poster, but having it on the back doesn't amount to anything with regards to trailer stability, at least in the configuration we use.
rgds,
WT