Your work looks great, but personally I wouldn't have a metal battery box for my starter power supply. Too dangerous for me! Sullivan makes a neat molded plastic battery box, and metal attachment straps. It was designed for Nicads, or NIMS, but can be used with Lipo's. I bought the straps from Sullivan, and made my own plywood battery box. I use two 7.2volt (6 cell) RC car battery packs. I won't go back to a starter with a power cord. Self contained is the only way to go. When this pack dies, I'll probably change over to lipo's. Good luck with your aluminum battery box, and be sure to use some good insulation.