Hey Pace,
Your friend who was used to multi crew operations didn't do you any favours there did he? It's a fairly basic principle of multi crew operations that the non-flying pilot doesn't just do things on his own (unless the SOP says so) without waiting for an order from the flying pilot.
Big Pistons, agree that it's the most preventable accident there is but, at the same time its also one of the simplest accidents to get involved in. A very interesting paradox! If it were truly "the most preventable" then it wouldn't keep happening! The only way to make it "preventable" for individual pilots is strict cockpit discipline (as you were taught by your instructor) plus an acknowledgement that it can happen to any or us at any time.
Glad to see the crew apparently unhurt in this incident and I'm sure the aeroplane will be repaired and airborne again quickly (albeit expensively!!).
Happy landings (with three greens!)
3 Pont