Most important point is that the batteries are secure and will not move, along with the cable- wiring in the area, box is not so important, as fiberglass compartments will resist acid sufficiently so the box is pointless. Most all these anal rules are for the manufactuerers and lawyers. Their not meant to regulate home DIY mechanics working on their own boats therefore are uninforced and coastguard boys are not qualified mechanics so do not have any legal standing to issue you a citation on the quality of your battery system.