Burstner Argos 747

Hi all. We joined the CC yesterday as we are in the process of looking for our first MH. We want something big (6 berth) and we've been looking at the Burstner Argos 747-2. (I have C1 licence entitlement).

I think I've got my head around the different weight limits but I've seen some of the Burstner Argos 747-2 described as a 5te vehicle with a 1250kg payload and others saying its a 4te vehicle with a 750kg payload. Is there a reason why they are different please?

I believe the payload already has the driver accounted for (75kg) and 90% fuel. If I added 100litres of water that would give me 650kg for 5 passengers and everything else. 

Has anyone got one and travelled with 6 adult passengers please? If so, how close to the 750kg do you get please? (Or is 750kg easy to stay within) 

Thanks in advance

Paul