Welcome, Larry!
I’ve also done a fair bit of tent camping, backpacking, kayak touring, along with car camping. I’ve slept in the back of a Subaru, a pickup canopy, a van, even a VW Beetle (made a bed that rested on top of the passenger seat backs from the windshield to the rear glass).
My current 13’ Scamp- small, simple, and non-self-contained- is an accommodation to family life as well as the vicissitudes of age that make sleeping on the ground less comfortable than it used to be.
There are a number of other molded
fiberglass options, new and vintage, that fit the small and minimalist profile. New:
Scamp,
Casita,
Happier Camper,
Armadillo, Outback, Relic, GoBE, Weiscraft. Vintage:
Boler,
Trillium, Hunter,
Campster,
Burro,
U-Haul, and any number of less common brands. The website fiberglass-rv-4sale.com collects molded
fiberglass listings from across the US and CAN.
Fiberglass or no, best wishes finding the right equipment for your future adventures!