The only time I have ever dumped the cabin pressure in any aircraft, was during the endorsement, when we had a near sea level cabin, and a diff of only about 2psi (so was roughly only a 2,000ft change in cabin altitude). Barely felt it, but enough to know anything higher would hurt!!
Dumping the cabin pressure when you're above 10,000ft, that's just calling for disaster.
As many wiser pilots than myself have said, "why turn a simulated emergency, into a real one?".
morno