I had a front uni explode on the start line at the drags many years ago, I had a loop in place which held the shaft from dropping away, the yoke in the back of the gearbox smashed the shaft about inside the loop until the loop was smashed against the tunnel and the tunnel was looking like the surface of the moon, all in about 3 seconds. The loop held and stopped the shaft from coming through the floor but in this situation it would have been better for all parties if the loop wasn't there and the tailshaft could have dropped onto the ground...so not so good for a stationary failure[:0] In saying that I still wouldn't run without one