Hey, i though of doing something similar just on the other side (in the first aid kit hole). I had the same resoning you did. But , as another member pointed out to me, the gas arms that hold the door up were set to hold up just the door. So, you'd need to upgrade them to support the added weight of your sub and box. But, if you end up doing it, post some pics, specs, and costs if you can because, like I said , I'm interested in something similar.
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Does not the fire need water too? Does not the mountain need a storm? Does not your scrotum need kicking?