The legality varies from state to state. You'll need to check that before attempting. Usually you can't legally tow more than the combined GVWR of your tow vehicle, which usually puts most 1/2 tons out of game.
Remember, the issue isn't moving that load with your 1/2 ton- it's stopping it. Your truck is considerably lighter than a 3/4 or 1 ton truck, which allows the trailered load(s) to move the truck around more. Also, your truck doesn't have as much braking capacity as the bigger trucks- even with a healthy set of trailer brakes.
I've got a 3/4 ton tow rig, and wouldn't personally attempt to pull doubles.
Ryan
