Are these suitable for under 3/4" wood or a metal panel?
That is actually personal preference.
The shorter sticks will bottom mount, but be a little short for most people.
The longer sticks will bottom mount fine, but the ball on them travels farther horizontally because of the extra stick length.
I split the difference on mine, and routed the shorter sticks in 3/8" on the bottom of my panels.
That gives you 3/8" longer sticks above the panel (vs. the 1/2" of the truly longer sticks), but keeps the arc that the stick travels at the shorter stick diameter.