I've added D13th Universal string sets to the forum store. They are made from GHS Cryogenic plains and GHS Boomer nickel wounds. These are the same strings that Johnny Cox uses. Here's the link:
<center> https://www.steelguitarshopper.com/d13t ... al-tuning/
GHS doesn't make all of the wound gauges needed as cryogenic nickel "Subzero Boomers". I include the .026 wound as a cryogenic to smooth the tonal transition from plain to wound. I've been using it on my D6th copedent and it works well.