I am counting the days till I go to Newfoundland to train on the Pelagian.
I own three sets on mk25/s600 regs and use them as back gas reg on open circit. Diving in the St. Lawrence year round, Newfoundland and the bottom of Lake Erie I have only had one of my regs free flow, was a 1st stage free flow that happened five dives in a row. Having the reg serviced between every dive by a "certified" ScubaPro tech. Feed up, took it to Dan at Dive Tech and found out it was tunned inproperly. That was three years ago and I have never had a problem since. I do not dive in Mark's range, but have had them in the 200'-180' range in 35-38 degree water many times.
Just my two cents (U.S. so that is worthless)
Erik