What is the best second stage for very cold diving?:
I need to upgrade my regulator to minimize the risk of free flow in very cold (fresh) water. I have a Conshelf/Sea first stage for which I can have an environmental seal added. One local expert suggested that regulator technology hasn't really advanced much over the past 30 years, so the best solution for the second stage would be to get an old metal US Diver one. These are supposed to have superior heat sink characteristics compared to modern second stages.
Someone else said I should stay away from old metal second stages - they are hard to find parts for, have no Venturi adjustment, and are just not as nice to breathe from as newer equipment. He said I should make sure to get a balanced second stage with heat sink features.
Does anyone have an opinion on this question?