The old Freeper Foxhole ping list would overlap with this one. Since it isn't very active right now, you might want to ask SamWolf or Snippy_about_it if they'd like to ping their people to one of your threads to see if they are interested in signing up for your ping list.
Yes, I went to the Foxhole before this ping list started. I have also sent a request to SamWolf or Snippy_about_it for more information. Thanks for the ideas.