The first thing to do is put the clear cover on the box.
I then mounted an exhaust fan to the box. This went smoothly, but I had to work hard to get the bolts through the exhaust fan box and into the studs in the battery box.
I then dropped the front half of the box into place and ran a bead of sealant along the seam. I then tried to fit the back half of the box into place and found it wouldn't fit. It needed about 3/4" more space, so I gently bashed the top of the rear firewall with a rubber mallet back enough to make it fit. I cleaned and re-laid a bead of sealant, then fit the rear box half into place. I put in the hold-down bars and tightened them down to lock the seams until the sealant cures.
I then hooked up the +12V exhaust fan wire, which was installed earlier. The problem is the way the terminals are set up on the exhaust box, it's easy to get the bolt shaft to spin while tightening down the nylock nut. The head of the bolt is impossible to get to at this stage, so I just tightened down against the top nut, locking down the wiring, but the bolt itself is a little loose in the hole. I think I'll put some sealant on it to keep it from moving around too much. This exhaust fax terminal mounting methodology really needs to be re-done from scratch.