what's up guys

here's the thing: AF servo by itself works great for tracking with center AF point. AF assist from my flash works great to illuminate to get focus lock.

but i can't get both to work at the same time. i'm going to do some run way shoot where the chicks are walking straight towards me and while i can get AF assist to fire, by the time i press the shutter, they will have already moved away from my AF lock, if you know what i mean..

so i am going to have to man it up and manual focus? which is less than ideal because it's dark and i can't see shit in my viewfinder anyway :|

any suggestions?