Okay, so I redid my way of doing z offsets and got slightly different values. Then I read your method and tried it as well. I got a curve that looked identical so I had some reassurance that my numbers were now correct. I then hooked up my crossover and the graph matched well enough.
I think the inconsistency could be due to the alligator clips I was using because I measured them later and they were about 1ohm each.
The problem with the measurement is that the tweeter was in phase with the woofers when I did the measurement, not out of phase like in xsim. I measured it wired our of phase too and got a large dip again, so I’m pretty confused. It’s not impossible that something was wired wrong but I checked like 20 times and I’ve never had issues with any of my other builds. Maybe the tweeter itself is marked incorrectly but I’ve used it before without issue so I don’t know.
Overall, I got the response I was looking for but I’m still unsure.
Every other build I’ve done I have used an extra inductor and a notch filter to get the desired phase I want and maybe I’ll just stick with that. I’ll definitely have to try it on something else before I plan something based on an inverted tweeter design.