Maybe you can set me straight as well, if you try out for M&D and make the black or red, and decline you are blacked balled from M&D?
This is pretty much correct (I'm sure there are some instances where girls tried out, made it, declined, and tried out in the future and made it - most likely absolute studs). When you sign up for M&D tryouts you are agreeing to accept a spot if you are offered one. Obviously not every girl does accept so very little chance of them making it in the future if they tryout again.
