Started working on the install just the other day.
I was able to get the battery pack in by jacking up the GEM, then wheeling it under on a dolly. Next, I lowered the GEM as the pack went up through an opening in the frame just behind the battery tray. The battery still needed to be raised up a bit so I did that with levers and blocks. Finally, I gently slid it into the tray & onto a vented rubber mat that I trimmed to fit.
I talked about using a bin to protect the battery but that did not end up being a good fit. Instead, I built a custom box from 11" wide x 3/4" thick white plastic Trex boards. The top cover is a fiberglass sheet. I am going to add a foam gasket seal for the top. There are also aluminum louvered vents front & back for heat dissipation. I do have the temperature probes from the BMS so I can monitor the internal temperature. If the inverter, for example, generates more heat than anticipated, I could add a duct or a case fan. Before, the tray just had batteries, so a spray, or dust, or pests was would not have been a problem.
This will shield the battery and all the electronics I am adding from the elements.