Hi Mike,
I’m also using Herbie’s threaded stud gliders. Actually I started out using the standard gliders and then switched over to the Giant
Stud Gliders as they made my U890’s more stable and easier to move with the larger footprint. Can’t say as I heard a difference between the two but then tweak differences have never been my forte, YMMV.
One other concern, at least in my situation, is ceiling clearance as the other types of footers are much taller (1.5″-2″) than the Herbies(.6″). Although my SL’s are in a vaulted ceiling area if I need to move into the 8ft ceiling area of my room they would never clear with the other brands. Moving them is an experience as I’m sure Tom knows as he has owned 845’s-945’s in the past.