Not sure. If you're flying somehting outside of the weight limit for park flyer (not hard to do), then you'll definitely need full. If not . . . It depends on the event and they haven't said. My understanding, for most big events events it would be a hesitiant "No", but again, I'm not sure about FTFF.
Keep in mind, this is your insurance in case something goes wrong. If it does, and you've got the full membership, you're coverd up to $2Mil. If you've got Parkflyer and you've been flying something too big, the liability is now fully on your sholders.