Specifying thread root for an internal thread.

[sociallyinept]

I am modeling both a screw and a nut to visibly show the interactions between them, including backlash. The thread I must use is uncommon, a .125-48 Unified Form, class 3A and 3B. Therefore, I am going off of the thread form equations in the standard, ASME B1.1. What I am having trouble with is determining the dimensions of the root of the internal thread. I need to have the major dia. of the nut at its maximum to get the worst case for backlash. Figure 3 of the spec (pg. 5) indicates that the root of the nut will be at the maximum major diameter of internal (which is 0.125) and the width of the flat will be at 0.041667*P (or P/24). When I make the model at these dimensions (and the maximum minor diameter at 0.1092) it looks wrong.

Any ideas?