Battery Box Rating in 3250 Cardinal

[Havasu Bill]

Good morning-
I just purchased a new Cardinal 3250 after selling my coach. I'm use to being able to have unlimited power when boondocking with the coach so am trying to feel my way into the fifth wheel life style.
The battery box in the 3250 is built into the floor in the front of the 5er. It comes with 2 group 27 Exide batteries in the recessed plastic holder.
I want to put solar on and change to 2 GC2s.
I sent FR a note asking what the battery holder was rated for so I didn't overload the box. The response was that it wasn't rated but was designed for group 24 batteries.
Has anyone dealt with this issue yet and come up with solutions on how to best install 2 or possibly 4 GC2s?
Any thoughts on leaving the 2 group 27's in the current box and add the GC2s next to them?

Thanks for any thoughts on this.

Bill