The house batteries in the XV-JP Rubicon are on their sides:
In general, VRLA--Valve-regulated lead acid . . . that is, sealed as opposed to flooded--batteries can be placed in any position except upside-down.
The amount of hydrogen produced by these batteries when recharging is less than for flooded cells, but best practice still suggests that there be top ventilation available to prevent hydrogen from accumulating in the battery compartment.
2007/2012 custom Jeep Rubicon expedition motorhome
2004 Jeep Grand Cherokee
2006 Honda PS250 Big Ruckus Expedition Scooter
1996/2002 Honda XR600R highly-modded