Acoustic coupling and mechanical coupling are not the same.With Casters off I have 6 sq. ft. on the stage - You can feel the stage. ( Bare wood stage ) Casters on 4 pts on stage not so much.
Depends alot on the stage - I've played carpeted stages with no effect.
And if your cab is vibrating that much, it's not braced well enough. That's a waste of power.
+1.Your mistaking physical coupling with acoustic coupling.
The bass is still fine in the audience even if you don't "feel" the stage anymore.
Exactly. And you really don't want that much mechanical coupling.