I note that Giorgio Romani and Richard West, both remarkable hollow form turners, use gates as their only support in even big and deep hollow forms. West uses an Irons Gate, Romani's is homemade, similar to the one pictured in Alan's posting but with a shallower gate. I quite like my Irons Gate, but I am not brave enough to use it for larger/deeper forms. My impression is that, for hollow form turners who don't want the constraint of a guided system, the gate gives just the right amount of control in otherwise "freehand" hollow form turning.