Usually, my homebrew parts start as a large thin crust industrial pizza pan from Pizza Hut. I took a stack 25 years ago and still have some left.
Cut to shape, sand off the grease, bend in a vise and voila! It's great aluminum - not structural grade, but fine for battery trays and what not. Polishes up perfectly.
Having said that, this is some angle bracket I found when I cleaned up the basement. Just happened to be the perfect size. I have foam to keep the battery from sliding, and velcro straps of course, but I'll add that stuff after I paint.
I ran this body on my SCX10 previously, though it sat much higher and ran with 4.5 Pitbulls. Looked good there, not sure why it looks so off to my eyes now....maybe I've been spoiled with all the huge full size bodies that are out now.
I've got another body on the way, once it gets here I'll figure out which one to go with.