I'm about 6' and haven't tried to lay down in it yet, but I know others have done it.
My plan is to take out the back seat (and keep it for later), then build a wooden platform anchored to the floor. I would make sure to leave access doors for tools and gear stored underneath. It would be ideal to keep the 31x10.5 spare under it, but if it's too thick I'll just bolt it to the top of the platform and stick it outside when it's time to sleep.
I guess I'm just excited to try and make a mini-camper.
I'll get photos as the project goes on, but it'll be a couple weeks yet.
Anybody have photos of their setup?