Check out caravan campers. Used ones are cheap in Nevada and many have double rear doors. They look very sturdy.
Yep. I had a Callen on my F-250 which was nice,but this popup gets me out of the perpetual sun and other elements down here. I've got chronic back issues and that queen bed at night sure helps.Having owned a few pop-up campers as well as caps/toppers/canopies/whatever I'll just say this: it doesn't matter what you buy as far as putting your bikes etc inside (they WILL fit in a camper), either way, your going to be moving them out for the cooking, eating, sleeping times.
Personally I'd rather move the bikes or 'yaks out and then grab a cold one out of my fridge and sit at a table with the furnace on, then roll into a nice comfy bed, and make breakfast at the stove when it's pissing down rain in the morning than crawl into a metal box over my tailgate. Others however, may prefer to grovel...