Hi I think that insertion of the knife on exact targets is problematic. best. Think Soft places, Neck is good any angle,stab at the face. gets a real hot stove reaction.hopeful eye strike would be a show stopper. Soft targets in the abdomen abound,the kidneys and the belly button show up from front and side ALOT. Under the rib cage, going straight in or an upper cut kind of stab(this feels really natural),
Simply rolling the knife and play with cutting the hand of the grabbing hand(AFTER he's already got it not before.) . a good training partner will get it sometimes., sawing quickly back and forth will usually get the pull back reaction, Dropping energy like that found in Dumog like Wrenching or ww2 hand to hand stomping combined with sawing will usually get you knife hand free. Tried this many times WIth BIG guys with a complete dulled replica,It's the old Rattlesnake analogy and the Glass,With proper gear dull live blades i know it wastes some money But it will freak you out a bit because at that low brain you cannot believe it's not real, the rattlesnake analogy,(I collect and love herpetlogy and even if a Russels viper is on his cage and there is no chance he will get you if you put your hand up to the glass virtually everyone Pulls the hand back instinctively, or when the spitting cobras spit even if your wearing protetion you flinch.
Same with a "fake" knife sawing at you. Training knives are Great but we need better protective gear and SMALL SHiv like replicas to play with, i remeber seeing some. and we should play with these in out training. A philadelphia collar is good also if you want to be able to try stabbing the throat(amazing how much silat and FMA's are so hard to hit in the hand because we learn how to move them but train so much not considering the head. or throat. VERY good protective equipment is needed for this but try it. it's an eye opener.
Past that STAB STAB STAB.
Remember The weapons of the archipelagos a barong will lop all kinds of things off, but we don't carry those anymore, look at the viking swords etc from our western past. thrustin was a definite option but the good ole angle one or two done in a heart shaped pattern(reference dog brothers heart shaped pattern for full contact hitting, HARD to defend against a slight change of angle and the momentum will carry the blade or stick lower than expected still striking hard to the pelvic area or the knee. All golden shots with machetes and real swords,I do alot of jungle survival work and have to butcher animals up to goat size with edged weapons. and have machete's,and filipino weapons galore Plus some modern survial like knives with the neccesary chopping power to cut a bamboo bed(regardless of horror stories involving snakes and critters, just sleeping off the ground with a good quality mozzie net will keep them from falling on you and they regularly crawl under you at night, no biggie,
a small tactical knife even a really nasty one like the civilian doesn't have that loping off ability not even close it's just a different animal.
I tried to start looking for a comparison a small compact 38 or 380 automatic is very dangerous, but practical for our times same as folders or small knives, A barong would be akin to a 380 semiauto main battle rifle conceptually identical But training and application is night and day. While running the orchard in the countryside i meet and carry weapons that are agricultural blades Something you can use to chop and clear Brambles up to all kinds of things, Vicious chopping motions with these weapons are natural and common place, I also have a sawed off 12 guage At about 15 inch barrel Real small and handy but you can't carry that in the city obviously the city and a push dagger or small knive and a 380 auto or 38, different story all together.
I feel the most comfortable stabbing and the closer you can keep the knife to your own body the better same as gun retention, and stiff arm him in the face or neck they are hard to get away from look at foor ball or rugby etc.,the better is smaller (no punyo etc) the less leverage he can aquire from you the better while a 3-4 inch blade my personal carry might be 3 inches even smaller, plenty big enough to reach the right spots but very hard for him to find the leverage to do any kind of stripping moves, try it. We sparred and did stabbing defenses and disarms most training knives are so big they allow unrealistic access to his blade and the handle etc.with a small knife and you can't find a punyo and any stripping motion ends up in you running the blade across your hand or Wrist makes it pretty untenible just a few inches makes a real difference, this also makes a point inserting the blade, anywhere in the neck you'll reach the vitals, and puncturing the abdominal wall is your basic goal with belly stabs, the kidneys are only 2-3 inches tops from the tip of the skin so is the artery.
But these targets seem the most natural anyway and are common knowledge so i don't feel i'm giving away the goods.
again my rambling rambling rambling but this seems to be my experience.
Bon
P.S sorry about the grammar etc.