I had debated a lot about the placement of the door for this camper. I really liked the idea of a side entry door, but there's a few negatives about it that I just couldn't get past including head clearance when you enter due to the slanting walls, as well as inhibiting natural flow of the interior layout. I really like that the rear door, in combination with the departure angle, make it so you don't have to duck at all when entering the camper. It also makes it more possible to layout a nice symmetrical and functional interior.
One of the primary reasons to go with a slide in camper or a bed delete camper such as this is that it's much easier to seal the elements out of the habitat compared to working around a tailgate and bed tubs that leak like a sieve.

I designed the door frame to have a large flange that works in conjunction with a bulb seal to seal out the elements.

The door itself is built using two 45 degree support brackets and custom welded inner and outer frame.

In the first picture here you see the outer frame getting bonded to the two panel cutouts after getting sprayed with primer, and in the second main frame is getting bonded to the body of the camper.
Here's a video of the door functioning after getting everything mocked up for the first time.
As you might see in the video I decided on a type of full width waterproof hinge and I'm super happy with it so far as I'll be able to leave the rear door open in the rain without water pooling and dripping through the hinge itself.