John, I have a similar system on my B rapide. I do not use a tab washer as I think they were fitted more in hope than anger. I drill nut and outer spring plate and use lock wire. I really dont trust this system completely, but at least a look through the PD filler cap lets you know if the wire is still intact. Be a bit careful with that impact gun. I have known an instance where the hexagon has pulled straight off of the ESA nut as if it had been made of cast iron. I still use the impact gun, but carefully.
N.B. I have been informed by, my mate Russ, that I may not be entirely correct in saying my set up is the same as yours, in fact I could even be wrong! I have a modified "C" outer plate, with splines inside. Not a "D" Type.
John