will gr27 batteries drop in to 27FB?

After two years without batteries we're interested in some limited boondocking. By limited I mean only a few days at a time, but in a remote location with no hookups. I've just ordered the Zamp 200 watt portable solar charger and need to buy some batteries. I've read that people have upgraded from the group 24's that came with the trailer, to group 27s for slightly more storage.



I see there is a battery tray in the battery compartment of this 27FB. Will the gr 27 size batteries fit in that same tray, or does that need to be replaced to use larger batteries?