We have the Dometic B1900 fitted to our Outback Swan, and had it fitted by the dealer before pickup, not factory fitted as our dealer did a better deal than the factory.
It is fitted on an aluminum H frame and goes where the original roof hatch is. At 34kg, we are on the limit for raising the roof, but as it was fitted before we took delivery, the winch is still covered under warranty. Our dealer reinstalled the roof hatch about 20 cm behind the new a/c so we now have the best of both worlds. We originally had the Swan in QLD and it makes the canvas bed ends so much more comfortable, allowing a daytime nap if need be - we found it essential for our two year old to get to sleep.
We have run it off our Honda 2 and it does it easy - both cooling and heating, but the increase in engine revs will make you want to move the Genny after a while if you have it 10 metres from you. We only do it if we are camped somewhere with no one in close proximity. Being roof mounted, we have never had a problem with noise in a caravan park.
One thing to keep in mind, particularly in QLD, is the amount of condensate that drains from the unit when cooling on a humid day. Depending on the angle of your van, the canvas can be very wet come pack up time.
Hope this helps