I started my "formal" eskrima training under Edgar Sulite's system, Lameco. Edgar used to talk about knifings in the Philippines, one way was to put a bottle in a paper bag, shape the bag to the bottle, take the bottle out, then put the knife in. It looks like you are holding a bottle in a bag. This was done, he said, when you moved through a crowd so you could get close to the person then stab him, the blade punches right through the bag. Another instance he talked about was a local boxer who was messing around with a local guy's wife. He said the guy knew of the boxers reputation so came after him with a knife, he said they ended up in the classic side headlock position with the boxer punching the guy in the face, and the guy stabbing the boxer in the gut. He said the next morning the guy was in the hospital with his face hamburger, but the boxer was on the slab in the morgue. (Then he said "which one won", but that is another point)
I guess the point I am trying to make is, train for as many eventuallities as possible. Have your guys do scenarios where someone walks up behind them, where someone walks by them going the other direction and may or may not stab, where someone walks up and asks the time then pulls a knife and wants their wallet, etc. Re-create Noir's bar fight with padded sticks so students get a feel for chaos. I agree with both Hock and Noir and I think they are comming at the same conclusion from different directions. I have fights on tape where two people began duking it out, one guy started to lose, and pulled a knife, they were both in "athletic fighting stances" to begin with, now would you classify this as dueling? It depends on your interpretation of what the word dueling means.