Actually it's a done project.
Your estimate of weight, after adding all the components, to include the sound proofing on the fire box, is probably close to actual. We don't have much weight (except the gen) under the bed, and compared to may friends who like to store things like sewing machines under there, I don't think we have have as much there as others (we don't full time).
The lost space was hard to get to, and unused.
The vibration topic has been raised by friends many times. Some think it would add a special "twist" on the romantic side. Really though, it doesn't vibrate as this particular unit is very smooth.
Noise would be another issue with regard to sleeping, but it is very quite: even with my hearing loss of 82 percent in one ear and 80 percent loss in the other I can still easily connunicate with my wife while sitting on the bed.
Tha t said, I have never ran the gen while sleeping, as I think that would be very rude to others around me. In fact I will not run it before 9-10 in the morning or after 7 at night.
I love my install, that it is quiet and does not vibrate the trailer. Neither my wife or I rally notice it running from the front of the trailer.
I know that with it 'permanently' installed it goes where the trailer goes, but that's actually very nice. For example, we were on a three week caravan, where one day we had to wait for a couple hours for our camp spot to become available. We pressed the switch, turning on the gen to microwave some leftovers for lunch without hassle, or mess.