Cool pics! It's nice to see some detailed pics on techinque. I haven't gotten a chance to take down a tree that size yet with my AK, but I'll be sure to try out your tech. when I do!
To the OP: It is my understanding that you generally want to cut THROUGH the target. I've been in the martial arts for about 15 years now and it's always the same - punch through your target, kick through your target, thrust/slice/hack through the target (with a sword or knife), so I assume it's the same. That's what I do when I cut stuff up with my knives. Remember, your real target is about two inches to the back of what you're trying to cut. Think of punching a human in the chest - your should be trying to hit a point in space two inches or more beyond his spine.
However, control is important also. Indeed, it's the most important aspect of knife work. (or any kind of physical work really) Without control you're just doing what anyone can do - you're taking a big, heavy tool and swinging it with abandon at stuff. You're not really practicing safe technique and you're not getting out your full potential.
In the martial arts we have a lot of exercises for control. First and foremost is learning to practice new things
SLOWLY. Let me say that again -
SLOWLY. When you practice things fast you're learning to rely on speed and momentum to pull you through the motion. When you slow it down from there you'll find you've got all kinds of flaws in your technique. Start out
SLOWLY and continue practicing your technique slowly until you've worked out all the flaws and such. When you practice like this you're learning to rely on proper technique. Then you gradually increase your speed and power (in roughly equal amounts simultaneously) until you're where you want to be. If you start to feel sloppy or like something is wrong then you slow it back down and figure out where the error is. Even after mastering a technique you should still practice slowly as much as you can. Once you start to rely on speed and power all the time, even if you started out properly, you're just back at square one - Drunken monkey with tools.
Once you have enough control you should be able to pick any point in space and throw a cut/punch/kick/etc. with any amount of force and speed and STOP it right on that point. That's where you'll see your cutting improve. You'll start to pick points on the other side of your target and then cut through to the target.
Anyway, that's my opinion on the subject. However, like I said, it's mainly from a martial arts point of view. I haven't had much experience cutting with my HI khuk yet, but I imagine its the same. I've found I can apply all of my martial arts principles and philosophies to pretty much every aspect of my life.
Krimson Draegon