Come on... we build our TD's... so we should build our chuck boxes too. I'm leaning towards a modified BSA box design. The basic one they have used for many decades can be built out of one sheet of plywood and a couple of 2x4's I believe. That'll be cheap enough!
The Bluesky stuff is real nice but more than I think I need since I already have a galley in the TD.
Putting it on the tongue is a good idea. Cabela's now sells the current style stuff which is a fancy table/cook surface idea that is not so much a "box", just a glorified folding table affair. The few models that have storage use nylon bags that hang from the frames. None look like they actually store any gear when traveling. You empty it all when you're packing up, fold the rig up and out it in a carry bag. Seems self defeating unless all you wanted was a portable table. I want to have the capability of having a stove, dish pan, cooking pans, utensils, paper towels, table cloth, etc all in one place and one unit that I can load in the truck and place anywhere on a camp site as an adjunct to the galley.
And besides that...projects are fun! And being able to say you built it yourself when people ask is very satisfying!
99% of the way done with a Generic Benroy. Only because these might never be done if you like to tinker. But it's on the road!