Rowan, I was fortunate enough to get the plans from a local box manufacturer emailed to me to make a telescopic box 26 x 26 x 10. (The bottom half of the box fits snugly into the top half of the box). They wouldn't make the box for me as a custom box-too expensive. U-line sells a cardboard box of this dimension-but a 100 box order minimum. Home Depot sells a 4 x 8 sheet of coroplast for $23. I also found some plastic rivets to use to hold the box flaps altogether. Figured I use a couple of straps with quick releases and be off to the races. For the cost of the plastic, I'll just make one. If it ends up being too flimsy, maybe I can beef it up by laminating another layer inside. If it works out, I'll post pictures. Thanks for the words of caution.