Also try to get them centered above the truss, rather than all leaning forward twisting the truss. It can take the twisting, but it could really unbalance the stands. You might be able to use a C clamp and attach it to the back bar on the truss (the backside of the triangle it makes) and have the cans rest above the truss. In other words, from the front of the truss, go over the top and connect the clamp to the back of the truss and have light's hanger go up the back of the triangle then aim it down 90* so its facing down the front side of the triangle. Hard to explain
Here is a pic going from the top of the triangle to the front side for my pocketscans:
http://creativedrought.com/5centmonkey/2005.05.07/index.php?image=Img_8119.jpg Instead of connecting to the top, try the rear bar of the truss and go up, and the can will probably have enough hanger to clear the top of the truss and aim down, this will center the weight on the truss a bit better. I like to mark my mounting points w/ electrical tape so I use the same point each time and I dont chew up the metal screwing the clamp against it. Just 5-6 times around seems good. Might save your hands when moving it around...
--Kev