battery capacity

We are in the process of buying a 2013 lifestyle LS36FW, we are having a 2000 watt inverter installed along with 3 group 24 12volt deep cycle batteries. Most other coaches of this type I see that all three batteries should fit in the side compartment on the left side of the trailer. But he’s telling me that he is unable to fit three and that the third battery will have to go in the front storage bay, while I don’t really have a problem with that I would prefer to have them all together  in the side compartment. Whats the right answer here? Ideas?