Does anyone use/has anyone used, these? A few of our sub-rented lights today came with them. First time I'd seen them in person. Terrific idea. Imagine a tour leaving the clamps on the truss, ensuring that every moving light will be hung in the exact same place every time. Plus, one person can hang/unhang a 90 lb. MAC2000 all by oneself (but still not recommended, unless swapping a light in the air on a truss with a rope and sheave). If only the blasted things weren't so darn expensive. (And still didn't stop someone from hanging a light backwards.) Thoughts, anyone?