Storage instead of 3rd row

In 2012 I converted my 4 seater Hyundai Elantra simply by removed the rear seats and covering the exposed floor recesses with strategically placed pieces of 1/2 inch plywood. Instead of carpeting I used the interlocking 2'by2' squares of foam padding sold by Sam's Club, etc. These are comfortable to kneel on, dirt and water resistant, can be easily cleaned by removing them & hosing them off. In some of the plywood sections, I installed hatches to ease access to the spaces underneath. One nice feature of the Elantra is the space for the spare tire is large enough to hold a full size spare. The Elantra came with a cheap tire repair kit, and not even a donut type spare. For 116,000 miles I've been driving a customized 2 seat mini-station wagon. I'm 6' tall, and I've found I can lie flat on my back, on an air mattress, behind the front passenger seat (if it is pushed as far forward as possible). That space would be too tight for two adults laying side by side, as far as I'm concerned.