Taking any impedance measurement with WT2 or DATS gives simple text files. They might classify it with their own suffix, but you can rename any of them as text or other types of files after opening in a generic text editor. Most often the hiccups come from errant header info that might miss a " or * or simply isn't formatted as the program is looking for. That's really all the different suffixes are telling us... what the header info might contain.
I'll have to do some hunting through the thread unless anyone can point to a summary of how they are calculating and how many elements they are using for the complex Le model.
I know in my own experience, until you have a very complex model, the most useful results come from the ability to make adjustments to best correlate with a simple, near field measurement of the driver in a known sealed box or similar. Particularly where shorting rings and sleeves are used, you have to pick what parts of the curve you want to match related to which parts of the frequency response interest you most. I look forward to seeing what they have put together for the latest update.