Here you go, Yoda: Back when I carried a spare tire I flipped it upside down and dropped a Rubbermaid Condiment Tote (sometimes called a "Picnic Tote", bought at Walmart in the Storage or Housewares aisle) into the depression. The tote is divided off into 4 or 5 separate compartments to put spare parts into and keep them from moving around. There are two covers - One smaller, round one for the center compartment and another large one for the whole tote. I just drilled a hole through the tote to accept the hold-down bolt. The bottom of the bolt is a fancy "L" with a clevis-like attachment to the frunk floor.
I used the original donor spare tire hold-down bolt in the frunk to hold everything in place. My spare came from a full-size, rear-wheel-drive 1978-1979 Cadillac Sedan deVille which was the only model and years that had a 16" spare with a 130mm bolt circle. I pulled the spare, the hold-down, and a few other goodies from a salvage yard Caddie and it all cost me $10 bucks.
I had to delete the spare tire when I added my gas heater and lost the space to store it, but I still use the spare part tote in the Frunk because it is so handy. The spare tire was mounted in the center and the bottom hung over where my heater now sits. The heater sticks up far enough that the spare tire no longer allowed the hood to close. I now carry a hole plug kit and a 12 Volt air compressor. Sorry for the funky photos - Blame it on Powerpoint!
