Bob,

The force by the mainsail driving the rig forwards is the cause of a pitch-pole. In addition, when the bows bury and stop the boat, the momentum of the rig adds to the forward-driving forces.

I am still in doubt:
If you want to depower the top section of the mainsail, the part that contributes the most moment (force*arm) to driving the rig forward, then would it not be most efficient to stall the sail?
When releasing the traveller (and mainsheet) you prevent stalling the sail when bearing away, don't you?

Your main advice bring crew-weight to the back of the boat, I assume we all agree on.

Thank you for a most constructive answer!

Stein