I am not envisioning your term 'cutouts'...
My fifth wheel area where the batteries are installed has elongated area all across the front on the battery compartment completely open to ground below. My batteries are installed with the plastic case with lids with holes in bottom for drainage and vent tubing of the removable lids. Something like this from GOOGLE SEARCH.
The battery install area should allow for drainage of battery fluids in the event the battery boils over from being overcharged.
The battery install area also needs to be vented to the outside for venting of the battery fumes when being charged. The fumes are very corrosive and will eat up anything metal around it.