G'day ranger_ant,
Just something to think about before buying the Duoetto, they are well priced for what they offer however they do draw 25amps on 12V and 4.6 on mains power.. This is huge when you are trying to conserve battery power..
The plumbing fitout with all the on board HWS's is very similar and all as time consuming as one another (Diesel, Gas or Elec)
Have you concidered gas or even if the budget doesn't permit, maybe a Aquacube or Coleman unit??