I looked at rib with rails but couldn't justify the extra costSame thought process as you, the fun is in fitting the bed for me, I also don’t want a fully kitted out van but the usefulness of a bed/chair is perfect for me.
I do like the idea of rails to move the seat/bed forwards and backwards as needed.
I also wanted the Rusty Lee frame as there's loads of storage underneath & it's the 4 cushion version that I wanted as I'm getting a memory foam topper which will store on the dummy seat at the back