When I had my trailer modified this spring, I had wanted to have three small dividers made, but opted for the one stud-wall, and two regular dividers. The stud-wall can be moved forward 20", so I could haul a stallion in front, mare and foal, then two others in the regular 22" stalls. Usually tho", I have the stud-wall back, to give more cart and cargo room, and haul three minis. I also had a removable ramp built as well, as I really don't like a step-up, especially for the minis. I can haul another cart in the living quarters if I have to, or under the gooseneck if it is dismantled...and my show cart fits in front of the gooseneck, behind the cab of the truck.
I lightened the pics so you can see a bit better, and they are all painted grey now, to match the trailer. I also kept all the hardware and panels so it can easily re-convert back to a two horse side-byside, if I decide to sell it, as the resale value is higher as a large horse trailer, than a mini trailer this size.
In my bumper-pull, all I did to convert it was screw some rings on the walls, and hang heavy matting between the horses. It is only be used for local trips, so that works perfectly well.
Hope this helps a bit more.