Harness & wagon fitting queries

[Nanno]

It's fine if the shafts are wider than the wagon. The biggest drawback to having it square will be that it's more likely to hit the wagon box on a sharp turn. On the other hand, preventing the wagon from being able to turn too sharply is a safety feature since these things can tip if they turn to tight. You'll just have to play around with it and figure out what works best with the materials you have. Good luck!