Check out the JE Labs link in my OP, there's an example for switchable impedance.
I didn't have the link there when I first posted, I thought I should include it because its full of info.
Thanks!!
That link looks familiar; I may have seen it when I first started delving into this a few months back. Unfortunately, the switchable impedance on my transformers isn't isolated to specific pins and requires switching leads; that's the monkey wrench in my works.