Popping back to the clutches for a moment, do they actually slip? I thought they simply selected one input or another but crucially, left an open system for the cable drum when neither were engaged. Unless it's a known fact, I doubt the clutches would slip, especially if they run at the pre-gearbox motor rpm.
The pivot point on the H-Stabilizer. Thinking about why it's so far back, I realised that using normal airflow, the system is virtually power-assisted. The tail then flies to a point where it is neutral again. Further movement, either way, will be assisted by the airflow. Sadly, either a nut/thread failure or a rouge input will be power assisted by such an unstable system.
In answer to Mac the Knife's comment about the wheels and cables, I'd commented before it's almost as if it was Boeing ethos, a promise to pilots, that they would always have that physical connection to the Stab. It seems painfully ironic.