I also saw this as I researched my lift-top. It has it's plus points as it's a hard side and the sides create the wind support once deployed. Full paneled so minimal leak points. Downside to me is it requires the assisted piston lifts due to weight of panels. You could do foam panels, yet I believe you'd end up gel coating them to stiffen them up enough to operate cleanly.
My thoughts were the E/W panels have standard hinges and the N/S panels have off-set hinges to allow the stacking (or visa versa). I tested this before I built my lift-top and ended up abandoning this system. For me (and I mean what worked better for me) is the Aussie system of a N/S folding hinge (my lift points) and a flip up support on the E/W sides.
I'll continue to search it, but I found someone that did this system as a hard side with folding panels N/S and lifting full panels E/W.
At 2:30 you can see the brace on the east wall and then the folding lift brace on the north wall. As I said, this is an Aussie system that I adapted for my use. No gas pistons or spring assist required.
https://www.youtube.com/watch?v=q4byZJ4md04&t=171sI also decided to go soft side due to the space the stacking would have taken up and deploying from the outside only. My issue my not be yours due to mine is on my truck camper. A towable is easier to work with from the outside..
I will be following your build!