After contemplating twenty different directions to go, finally said screw it and used the plastic battery tray I have. Went to the hardware store for some spacers, then drilled 4 holes in the well floor. Installed some rivnuts, then mounted the tray. Seems pretty secure! I'll have to fab a cross brace for the topside, but I'll wait until I sit the battery in there.
Part of me wants to work on moving the wiring and such now, but it's a beautiful weekend here in KY and if I wanna just take off i won't be able to. I'll probably wait until Monday as I'm working next weekend, and waiting on some buss bars to come in next week.