With a single edged blade, I prefer to use it in Reverse Grip, with the edge facing towards me, so called Edge In style. This deals with only gross muscle movement, and not fine motor skill (which we know goes down the toilet when the adrenaline hits and suddenly you're fighting for your life), as it is simple stabbing, and pulling. You stab in, getting the knife to depth, and then pull it back towards you, cutting your way out of the offending tissue. Fast, and powerful way to go about things. Its pretty well accepted (and I dont want to start a flame war on it) that thrusting gets quick kills better than slashing, I see this as the best of both worlds... get to depth, and then cut out, widening your hole... one nice big stab wound, in effect. Also, in folders, doing it this way eleminates stress against the lock, that comes from slashing across, and then stabbing back, in edge out reverse grip... infact, it takes stress all off the lock, and puts it all on the stop pin, because of the angles involved, and the fact that you're never putting any pressure against the spine of the blade.
As for holding it in forward grip, I have till this point, used an edge down/edge towards the enemy type hold. Recent purchase of a Steve Mullin clip point fighting knife (with a sharpened false edge) has me giving a little more thought to holding the knife "upside down", but only in a blade with a clip point, and a shaprened false edge, because of the damage do-able by slashing across with that concave clip, and then stabbing in and jerking out with the main edge.
I think there is something to be said for doing it that way with singled edged knives too. I know of an instructor (forget his name right now
) who teaches people to fight using Spyderco Enduras and Delicas (his choice for folders, but his material works with any folder), and teaches/prefers both Edge In reverse grip, and Edge Up forward grip. One of the things he teaches is to go low, between your opponents legs, and stab up into the area of the rectum, and then jerk the blade forward and out... done fast of course, and you'd have to have the right opening, but it would be a nasty technique. People can also clinch, and ball up, turning away from you, for just a split second, when injured, and that provides an opening for a similar shot, this time done from behind, just up/in and out... with a long enough blade this can be fatal. "Rectum? H*ll... it kill't 'em."
(Sorry, couldnt resist.)
Ahh... nothing like a lovely, happy, post about gutting people to introduce oneself to a new forum.