What access do you need to change the oil and perform other routine maintenance on the generator? On mine (a completely different model), the oil drain is on the underside of the generator, with a little access panel attached to the outer cover. It wouldn't work well to have it installed over an unbroken floor. Likewise, there's the need for the exhaust plumbing to exit underneath. The generator appears to be mounted to an angle iron frame, which is bolted to the undercarriage of the motorhome, so far as I've been able to suss out.
I guess I'm suggesting that you consider removing the floor of the compartment and see if you can't find a way to make it able to be raised/lowered from underneath, rather than slid in from the side/front. Of course, for routine maintenance and such you'd just leave it in place.
Do be careful to seal the compartment thoroughly from the interior of the trailer, and maybe consider adding some fire/sound insulation.
