Although it's not for everyone because of the price, I can echo what I've seen others writing about an anti-sway hitch like the ProPride.  We've got a single-rear wheel, short bed F350 towing a reltively rear-heavy 35' trailer.
The hitch performs amazingly.  We've honestly NEVER felt any movement from big rigs passing us either in our direction of traffic, or against it.  Even the movement that is caused by strong winds is minimal.  I don't believe that there's any such thing as 100% elimination of sway/movement - after all, a strong enough wind can move anything around.  But a good hitch can go a LONG way in making the tow much more relaxing.