Dennis and the Double Leg

I have a hard time with the sort of double leg shoot that Dennis Kang, a top middleweight MMA fighter, does in the screen captures below with perfection. Specifically, I'm wondering if I have to drop the lead shooting knee completely to the mat, or is the deep lunge enough.

I remember watching Cindy practice this takedown in laps around the mat months ago. I think I've got a pretty good shoot, and can change levels pretty well. But dropping to the knee in this particular move remains a problem for me. Working a little bit with the deep lunge, I think I can get deep enough--and explode upward strong and fast enough--for this move to be effective without the knee drop. But we'll have to see as I try it in training.