It seemed pretty simple to me. If you don't have a rulebook event, are not doing strickly demos, and are not catering to a select group of people, it would be a non-rulebook (class C) event with the restriction of only helis being flown that day. When we do the speed rally, we do class C since it isn't a rulebook event but restrict the event's activity to doing speed passes.
We also add that we will do buddy box instructor flights.
For our pylon race I entered it as a class C but when the sanction came back they changed it to A with restrictions since we were following 424 so closely. My thinking in going in as C was I didn't want to deal with the anal crowd about every little technicality under 424 (wing numbers etc) but I'll work with it.