I just retested, it will hold for ten, good, hard, completely inverted shakes by the strap, not touching the sheath body at all before coming out. With a belt wedged in there, it's a bit stiffer yet, and if I'm truly worried, I can tuck the pinky lanyard in my belt, or I suppose a ranger band could be employed here if I felt the bushwacking was going to get crazy, or I had planned on running somewhere (I only run away from things and very rarely by choice). I have yet to have it come out without intending to take it out, although, admittedly, I only have a few miles hiking and scrambling with it so far. For inverted carry, I could pretty easily make a different strap to include a small retaining strap. That may be my next improvement, a large Y shaped strap, one leg for the belt and one for the retaining strap, hmmm... Great, now I'm second guessing my own craftsmanship...
I just wet molded the leather with 'great intention'. The sheath started out completely flat and sewn, then carved a rough shape of the front of the grip out of a 2x4, got the leather wet and literally hammered it in and stretched the leather around it, then finished shaping with the actual knife. Let dry, rewarm/rewet/refit, cool, rewarm/rewet/refit, cool, rewarm, beeswax, done. Here's the money shots.
Cheers, m.