On my lightbox, (outlined here: A DIY UV post-cure Lightbox you too can make ) I used these adjustable felt feet: http://www.homedepot.com/p/Everbilt-1-in-Threaded-Stem-Furniture-Glides-with-Felt-Base-4-per-Pack-49908/203661113
What’s nice about them, is they don’t grip the surface, and allow easy spinning adjustment. They are not 6-32 though, so cannot go into the Form1+ directly. You could simply put them into a piece of plywood or MDF and set the form1+ on it though…
-C