Jeremy,

It shouldn't be necessary to put a contractor unit on the back -- many
would fit into the APU compartment:
http://www.gmcmhphotos.com/photos/g5330-troybilt-generator-installation.html

You should have looked at, and listened to, my Troy-Bilt generator at
Dillard. It is, admittedly, noisy, but not bad inside. Better mufflers,
or perhaps a Gen-Turi-type tailpipe, would improve that. It's a very
reasonably priced option (