I love those Merkel Helixes - how do they hold up in minus stupid and high humidity? We had a few really bad days here in Alberta that would maybe cause me some worry with that straight pull rotary action over a normal bolt that you can get some purchase on.
Mine's worked great over the past three years with zero issues.
I'm in Ontario, so we don't get the cold you do, but this year was ice/rain and snow all week temps from 1* to -20*