Taking the next step I took N5IB's advice and took the impedance calculations to completion. I'm not sure if the VNA will do this for me, but for now I constructed an Excel spreadsheet where I can just plug in the values the VNA gives me and get the final results. I've checked the calculations a few times and don't find any errors. The results still puzzle me. Some of the numbers I can rationalize from the actual behavior of my ATU but then some of the numbers don't make sense. I may be doing something wrong, or maybe there is some sort of voodoo going on in my wires.