I really like his designs. I got to thinking about his "step in" model that is only 48" tall

Didn't seem very tall (I'm 6'4") so when I got home I grabbed my tape measure to see how it compared to the Geo Tracker I was driving.

Hmmmm, interior height of the Tracker from floor to headliner was just a little under 48" and I have sufficient head room with the bottom seat cushion measuring 12" from the floor. As far as door opening width? No different than getting into the back seat of a 4 door car. One door should work fine since you don't have to crawl over the other person in bed, you can actually "shuffle" across the foot of the bed with your feet on the floor. AND you can take your shoes off AFTER you get in.
Jonathon at Rustic Trail has some great thought processes

Minimalist design with a good price. Kind of wish I had built mine minimal and added to as the need arose. After finding his website a month or so ago, it got my wife to thinking as well. Originally, she was in "no mood" for me to build another camper. After putting around 15,000 miles on ours, we have got a good idea what we need and what we can leave at home. The only addition she would like is access to a potty in the middle of the night, which, with the Rustic Trail design, could be incorporated without much effort. We don't spend much time in one spot so sitting up the side tent is kind of a bother. While traveling across N. Dakota we even spent the night behind a C-store, a potty would have been real nice there since it wasn't a 24 hr store. 12V would be a must with our travelling habits of stopping wherever whenever and would be no big deal to add. We don't cook much if at all (no, we're not junk food junkies

) I'm thinking 5' tall would give a lot of under bed storage. Maybe even an access door in the back for the under bed storage? Big pull out drawer? Great place for camp chairs (that we never get to use), pop up canopy?
Don't count anybody out because they have a different design or we'd all be in trouble.

(Not trying to start an argument or hurt any feelin's

) Some, like us, may not need or want "bells and whistles" just function.
Have never personally seen a Rustic Trail Camper nor have I ever spoke or conversed with the owner.
This is all IMHO and I realize nobody asked me.
