moss and oldtimer: Many thanks.

Great recommendations! Let's see: Be consist, i.e. "no flip flops in trees" (good tree-climber wardrobe decision, too?); tailor your climbing _style_ to accommodate when you're tired; commit to safety and be responsible for maintaining safe habits and systems. Please correct me if I've misinterpreted either of you.
Having said all that, I believe that climb-rated (23kN+) screwgate carabiners, double-auto-locking carabiners, and stainless "screw_link_s" are secure.
I believe that still unanswered question is, "Can a screwgate carabiner be "properly closed" to adequately prevent un-threading and inadvertent opening?". No, say the pros.
Vibration, friction, shock. I believe all these types of forces should be considered as potential methods for thwarting a gate lock.
I think that something like the Tory Red Cap Finger Tips (http://www.toryinc.com/) might be adapted to reduce the tendency for the screwgate lock to un-thread. In fact, I'd say there might be a size that would be adequate to similarly reduce the ease with which some have said that they can thwart the double-auto-lock gate. I'll probably buy a handful, strictly for the ground-_base_d laboratory environment, and see what they'll do. OK, here's the disclaimer: This mere speculation on usefulness of a specific technology is in no way a recommendation to any climber to use any product referenced.
Thanks again.