While I was training some kali a couple of years ago, there was this practitioner with about seven years of training under his belt, and a new kid with a BJJ background. Three times I saw this exchange when they were practicing free flow together: The younger guy felt like he had an opening for a takedown and he took it, then he would try to go for an armbar....you would hear the older guy hit the mat and you would stop what you were doing and glance over, and see him tap quickly. Then, as he stood up, the BJJ kid would look down between his legs and see one of the very long, straight training knives right between his legs pointed straight at his jewels. The older guy would always say rather loudly, "Oh, excuse me, it looks like I dropped something, could you hand me those?"
This group had an adage passed down from one of their head people to the effect of, "Most fights may go to the ground, but they stay there exactly as long as it takes the faster guy to get a reverse grip [on one of his knives]."
Felix Valencia of Valencia Lameco (private trainer to the CEO of Cold Steele) had one of the best
integrations of BJJ with a knife. I was so blown away by him in 2003 that I hired him to assist in the construction of the Defensives curriculum I was charged to develop at Frontsight in Pahrump,
Be well Cliff