I have a need for a rig where I can drop a 5D Mk2 approximately forty feet. in a controlled manner, down a shaft/stairwell. I've tried using a sling fashioned out of wire and then attached to a single line of braided cable. The problem I encountered is that the camera starts to spin uncontrollably. I also built a square rig with four points of attachment using nylon belting but the belting pays out at different rates leaving the platform to tilt. Any ideas welcome