does sealed off really mean sealed off?

okay, so I got the fuel cell. Now it's time to seal off the trunk compartment as per rules. Now does this mean that I put the correct thickness sheet metal in there and put bolts are rivets through it to hold it in, then totally seal it off with some sealant or something. Or? I mean does it have to be waterproof or airtight? I do have brake light wires crawling through there and on the other side I have the positive battery cable coming through, can I build around it and just put some kind of sealant in there?View attachment 20150204_094301.jpg

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