After much head scratching - this is how to program a throttle cut on a Futaba 9 (and most probably most of the other Futaba radios).
This came to me while fighting with the radio to programme a glider for the first time in my life.
Re-recorded with explanations and made longer and brighter.
Theory -
I am mixing the throttle (channel 3) back onto itself (channel 3) via a PMIX (#5 selected arbitrarily) with a -100% rate and 0% offset.
I am using switch E (a three position switch) so that the motor would be cut on TWO out of its three position - motor arming must be a deliberate act.
M