I think a floating cylinder may be best. The ionized gas is a cloud of Positive ions and a cloud of electrons. How they are layer with respect to one another has yet to be proven. If the body is grounded it will produce a voltage to attract both the electrons and the positive ions. I think the object is to keep the gas away from the wall and centered to push on the cylinder. Unless my thinking is wrong, I would float it, unless the behavior of the ionized gas is fully understood.
https://www.youtube.com/watch?v=UMJ3eCHZtGY