Usual preface, I’m with PreciseBits. So while I try to only post general information take everything I say with the understanding that I have a bias.
Hey cniemann88. The real issue is trying to find the “hybrid” nuts. ER16A in my (and apparently most of the industry’s) opinion shouldn’t have a 19mm thread. Simplest solution is that if you don’t need the hex head for something like a rapid change just switch out to the ER16M (mini nut) and you can find tons of manufacturers. I went through it over here if you want to blow half an hour.
The other major point in that is that any ER16 with a mini thread has a lower max torque. So watch out for that regardless of what direction you go.
Let me know if there’s something I can help with.