Those are great boxes, I really like the fact that you can build exactly what you need to fit your personal needs.
The only thing I would do different is I would not need wheels. I purchased a mini pallet jack several years ago so two or three four by fours glued and screwed to the bottom provides the clearance for the jack and it is much easier to move heavy items on the jack. Saves me money over time, I even removed the wheels from several of my machines once I got the pallet jack, have a large box of wheels in my storage building now

I intend to remove the wheels from both of my metal tool boxes when I get the time, they are just to heavy to roll around on wheels. I rarely move either tool box but there are times when it would be really nice to move the mechanics tool box to the other end of my shop when I am working on cars and other machines.