I see over on Husaberg.org that Aqualine is going to make rear saddle tanks for the new FEs - 8 liters of gas for a total of 16.5 liters with the stock tank. 4.4 gallons roughly. That would get me 60 miles into the boonies before I have to turn around and ride out.
I think that will be about right. Seal up the subframe for water storage.