Warren and Ben,
I have come to the conclusion that my entire scuba equipment configuration needs a rethink. I have acquired everything piecemeal over the past several years, and I have made the transition from mostly cold water to mostly warm water diving. I may just acquire two different sets of gear, one for cold and one for warm, rather than try to combine everything and compromise.
As for the knife, it is not so much a question of what to keep the knife in but how to attach it to me and how to securely operate the keeper with gloves on. I already have a Blackhawk sheath, but I don't like it. IMO, the Spec Ops sheath has a better configuration. Sullivan's may be an option for a special order, or an ankle sheath may work best. A forum member has graciously agreed to sell me a pancake flipper sheath, which I appreciate very much. I will just have to continue experimenting.
Now, let's see some more 16s!