Bobson, cool; I had seen pics but figured people wanted custom Kydex for a reason... no idea but glad to hear it seems to work really well. I think OWB under a cover garment is the ideal carry method for this kind of knife. Ahh, I think I know... the factory sheath is more designed for IWB it would appear.
Adam, don't take this disagreement the wrong way, but I don't think you are correct. I'm sharing this in the spirit of discussion, nothing personal.
First of all I think the underlying assumption that more positions/stances/moves are better is not necessarily correct. It's like alternating between EDC of a revolver and a semi-auto because you can: a solution looking for a problem. Further some of the techniques are likely to not work as well as others.
The idea that you will react quickly, diagnose the situation, and select from a catalog of many possible techniques (multiple concepts of how to stand, how to hold a knife, etc) also would seem to be overly optimistic, particularly when you have Hick's law (more decisions = more time needed to decide) and in all likelihood could be better at one or two high percentage methods (such as ice pick forward and reverse grip for example) and spend more of your limited training time getting *really* good at them.
That may be a bit unfair to you; I don't know you or your skills or really anything else, but I do stand by what I said; it may not apply to you though, and that's fine too.
Now, as far as specific grips and hand positions.
Practice forward and reverse... one of the great thing about that knife is that it allows really effective, powerful striking in either position, and the angle of the handle facilitates a locked wrist position. I think the knife is best positioned somewhere either hand can access it and then practice both types of draws.
I am very, very skeptical that a thumb braced against the back of the knife increases wrist stability. Even if it did I think it makes an unacceptable trade-off: your retention of the knife is palpably reduced.
Generally the argument in favor of the "sabre grip" you are using is that it enables more precision cuts or stabs, and that's fine: it does. But it also reduces the ability to retain the knife when unexpected force torques it against your grip.
I have never seen a training scenario where someone was totally unable to stab someone else with a small training knife for lack of accuracy, nor have I seen a scenario where someone's wrist failed and rendered their lower arm a limp noodle. But I have seen many people drop their knives or fumble the drawstroke or lose just enough grip that they begin adjusting their grips mid-fight.
Biomechanics studies seem to be with me on this. There are generally two types of grips, power grasps and precision grasps. There is an inherent tradeoff: more power = less precision. The thumb may be used to increase grasp strength (power grasp) or stabilize and facilitate precision.
According to Wikipedia citing Gray's Anatomy, when the thumb is fixed, the same muscle in the forearm also contributes to wrist flexion. If a concern is wrist stability, it would appear that securing the thumb in a fixed position would be important; I think the power grasp ensures this best, specifically wrapping the thumb around an object.
According to
this article on Cornell's site what you are using is called the "hook grip":
Hook grasp - characterized by a flat hand, curled fingers, and thumb used passively to stabilize the load, e.g. auto steering wheels. Load is supported by fingers. This grip is most effective when the arms are down at the side of the body. For objects with a diameter of 2" the hook grip strength can achieve the strength of a power grip. Very narrow handles decreases hook grip strength by pressing deeply into hand and fingers. Rigid handles should generally be avoided.
Bottom line: I think the icepick grip or a power grasp with thumb-cap make better use of the muscles in the hand and lower arm, and would urge you to experiment on your own, with your new knife, rather than go solely off of someone's word. But you should also consider evidence over anecdote.
