Thanks - that'd be great!
I might go googling her myself now and see if i can find anything
I'm sure you've found
Susan Garrett's website by now but I've linked to it anyway, do sign up for any updates, I think she is really really good. Sadly I really can't find the video I was thinking of, I think she only made it available for a short while before the course opened.
The gist of the video was that in agility when your dog is faster than you then you are not in the right place to give it the cues so it doesn't know where it is going next, because it is trying to look out the back of it's head and see what you are doing and where to go next and thinking it might be going wrong it is more likely to knock bars off. So you need to reduce the dog's uncertainty by giving clearer cues.
But...
because when the course changes direction you have to be right there to signal your dog over the jump and then to turn at exactly the right moment (without pulling it off the the jump you want it to take and without it flying over the one that is straight ahead) you haven't much hope of being at the next obstacle in time to give the cue there that would give your dog the confidence to know what it is supposed to be doing.
Sue Garrett's solution was for you to continue to use your arm to signal the dog over the obstacle while the direction of your feet tells the dog where it is to go afterwards. Because before your dog clears the jump your feet are already pointing in the direction you are going next it buys you a few seconds to get to the next obstacle in time. So your dog gets certainty and you buy yourself some time.