Errr...that was John that suggested scorekeepers--lol. If you had a target similar to the one you described, but fixed it so there would be no doubt that anyone that scored a 10 or 12 was cheating (without making it too obvious), you could call them out without actually calling names--make them feel like they were being watched, let them know that they had been found out. They might not come back, but who needs people like that anyway?

Long Bows Rule!