I just finished covering up some of the BIG holes SMB put in the floor of my van for the now-removed battery box drains. I've been meaning to do this for a while, ever since reworking my battery setup earlier this summer and removing the plastic battery boxes (see
viewtopic.php?f=14&t=9376).
I passively followed others' threads about mice getting in the van, and in the back of my head knew that was a big possibility since I had two big holes from the battery drains and one from where I removed the drain to the gray water tank. Last night my wife casually mentioned that she saw a mouse next to the SMB in the driveway. So, that made the project a bit more urgent.
I used some leftover sheet aluminum from when I capped my house fascia, silicone caulk to keep it tight, and self-tapping screws to screw the aluminum into the floor. Getting the aluminum to fit the curves and whatnot was a bit of a challenge, but it worked out.
I also cut a piece of screen to put behind the through-the-wall vent from the old battery boxes. Not sure how others' vans are set up, but mine just had the slotted metal vent and the slots were open to the inside. The small circle of screen I added should keep random bugs out.