Mine is a combo. Spare hold down, battery hold down and jack mount. I deleted the back seat, moved the battery and added the jack. The weight removed from the back seat area and added to the spare tire area helped the car to bite into corners and the jack looks kind-a cool. The plate is made from carbon fiber over honeycomb core board used for super light weight aircraft cabin flooring.
I install 4 10/32 rivnuts in the in the car and use triwing thumbscrews to hold the top cover down. The battery is mounted to another plate that locks into the spare wheel.