I build this battery tray for my track-only miata when i was on the factory battery. This is designed to keep the battery positively located so it doesn't shift around. I've had and know people who have had their battery shift under the bracket and the positive terminal short on the bracket. Some have resulted in a fire, I got lucky and it melted the bracket enough away to where it stopped shorting. Anyways, this model is intended to be used with the factory battery bracket and provide lateral support so the battery isn't just depending on friction to keep it located. Battery cavity dimensions (can scale if needed): 192mm x 127mm x 28.25mm deep. Designed to fit on an Ender 3 build platform. Front left bolt hole uses the factory M6 bolt location, front right hole need to drill and add a bolt+nut for a standard M6 bolt, rear two holes are for a 1/8" rivet + washer. Rear cutout lines up with the factory battery stop towards the front of the car. There is also a front hole that I used to zip-tie or mechanics wire down the battery hold-down... this isn't necessary but was a backup in case the nut walks off or J hook fails for some reason there is something to keep the battery held down.

I initially printed with 15% infill with PETG to keep weight down and keep it from melting under heat. It worked but would probably recommend putting more material in it. I only ran one event with this and ended up switching to a lithium battery so there is some testing on it.