What about terrain patterns or map objects as a visual aid? I.e. U know that U need to move your aim just a tiny bit to the i.e. strawberry object on a fruit map to hit the perfect hit.. Are U kindly gonna ask ppl not to do that too? ;x It's tricky..
Anyway, I understand what U wanna Mab, I've had similar situation few years ago when I wanted to add "no-notching" rule in bng here... I knew that it was complicated and that someone can hardly prove if someone was notching or not, and that it would bring too much bitching if anyone wanted to judge that even, but I still just wanted that rule to be stated. Just as a criteria.. as a standard..
It's the same with this visual aid thing, U can add the rule, but that's all U can do, ppl who use papers, monitor buttons, CD cases, self-made aids or w/e will still use it.. Because they can. Because no one sees them..
And btw, votes on poll are on your side, so just add the rule and stop giving away new ideas to youngsters how to cheat! ;x