I actually tried teh v5. Sorry, but that didn't work for me either. I mean, I didn't freeze...but I didn't knife. Maybe that was my fault. Probably.

Anyway, to the helpful part. I use v7. I turn it on, within UNDER 20 seconds, find and knife the player, and midway through, while your pushing him down, turn it off. Not when their right on the ground, but b4. And thanks to Bl4Ck.KiD for it.