I made this one 5 years ago and just used it today for a HomeDepot/Target run. The mistake I made was that, the structure, as shown in 2nd photo of the original posting, between the bottom of the box and the hitch, could hit the ground, or break the kickstand on certain turns. Had to change that area and it's a bit of a kludge.

The low CoG is great. Till the road slopes upward, you could forget it's there. But the design did require a well equipped workshop. I'm sure someone with fewer tools but more imagination could achieve a similar result.