I'm looking for guidance on 6GR qualification of box tubing in accordance with Fig. 4.28 of D1.1. Considering that the internal and external corner radii of box sections are usually dependent upon the wall thickness, would you still be required to have the minimum difference in wall thickness of 3/16" between the two test tubes as shown in the figure? I realize that there is a note that says that the tube with the restrictor plate shall be of the same size as the tube without, but it doesn't say that the wall thickness can be the same, the 3/16" dimension is still present with no notes attached to it.

Thanks!