To me, hold ups were minimal at most (I'd personally call it virtually zero), yes in previous track days it's been a constant pain in everyone who's faster ass. Taking flagging by the horn n waving the blue and following up with education via black flag + coming in for an explanation worked absolute wonders as did asking a couple of drivers to drop back into the rookie group. Once second session hit after lunch, super light traffic on the track.
I'd bet quickie refresher meeting before returning after lunch would only add to that.
Let's revisit if feedback warrants. Sharing of our experience n ideas will continue to make the event even better, please keep the feedback coming.