The other major step forward was developing a WDLR coupler. I've designed it to work in a Kadee draft gear box. I'm making a custom Kadee style box for the Kerr. This way I can use standard Kadee centering springs, and allows for Kadee/WDLR couplers to be interchangeable.
My WDLR coupler head is faithful, save for an additional vertical hole I've added to allow for coupling with a small staple. It's based on drawings and photos. Here is the first test print.
Note the heel of the coupler is extended in this version--I had momentarily thought of an alternate centering scenario for use on a WDLR bogie, but quickly realized that the Kadee spring solution was a good one.