Fiverwheel wrote:
If you're handy you could drill and tap a hole in the square tube and install a bolt to hold the bar steady.
The Swagman has a threaded tube hole, and uses a threaded hitch pin to tighten things down. It reduces the play somewhat, but since the inner tube O.D. is less than the receiver I.D., there is still some.
U-Haul has a retrofit version with lock (http://www.uhaul.com/MovingSupplies/Hitch-towing-security/Anti-Rattle-Receiver-Pin?id=16372). It has a U-shaped insert with nut that goes inside the interior of the inner tube, then you thread and tighten the bolt down before locking. Not sure it will reduce the play much, but might be worth the experiment.
The Hitch-Vise seems to be the answer. But won't be able to get it before we leave. I'll ponder whether there is something at the Depot I can use to kludge together that would get me by for this trip.