Air Conditioning for small caravan

Hi all, We have ordered an Eclipse Camper from Australian Off road campers, it is essentially a 13ft off road caravan with outside kitchen. AORC have the option of an under bunk Dometic Climaster air conditioner priced at $2500 installed. It needs a 2KVA generator to run it.

We are thinking that we really only need the bed area of the camper air conditioned for sleeping at night or for that afternoon siesta and to cool the whole camper is unnecessary when the main living area is outside. The bed is queen size and occupies the full width of the camper.

The air volume of the bed area can be minimised by fitting a barrier such as a heavy curtain at the foot of the bed and the poptop could also be closed to give an air volume of 2.2m L x 1.7m W x 1.2m H = 4,500 litres approx.

I have been searching for a low capacity/power aircon to cool just the bed area and have found that Waeco can supply separate compressor/condenser and plugin evaporator units for custom built refrigerators and freezers on boats. They use the BDF50F compressor and run off a 12v supply drawing a total power of 180watts. Cost is $1,350. Their website says this system is suitable for refrigeration volumes up to 400litres. Now, as a fridge will cool down to 0 degrees I am wanting to know if this system would cool a 4,500 litre volume to only 20 degrees?
The adjacent walls are insulated and the windows are double glazed.

If this idea worked it could be powered by our existing Honda EU10i. Even if 2 of these systems were needed there would still be a saving in $$, space and weight.

The items we are looking at are the Waeco Cold Machine CU-95 Compressor/Condenser and the VD-14 Circulating Air Evaporator.

Can any forum with experience offer their thoughts on this idea

Thanks in advance.
Les