Most of those pro dudes with eight foot racks have a noise gate in their racks that clips the signal just right, thus no feed back even if their feet float off along with their hands. I play a Jazz box sometimes [es335 copy] that tends to feed back mucho, but if you stand just right in relation to your amp and with the proper hand position you can play feedback like an E string. Tricky though; if it gets out of control it can rip your flesh like a weasel.