Dave, you have supplied the answer to my dilema. On the next trailer, I have been wondering how to keep boxes, buckets and tool cases from flying all over, without the use of doors. Seeing the way you have it setup is almost the answer for me. I think I would add a 4" x 3/4" block about 13/16" behind the face frame to create a slot. This would allow the 4" high panels to slip in and out of place easily while keeping everything where it belongs.
I'm big on using the trays that go inside buckets to organize and store screws, nails, fittings etc. I wanted to go 3 high with the buckets and was wondering how to keep them in place. This will be far better than bungee cords.
Thanks for the info.