You really would also want to have some sort of loss function, or at the very least a general idea of whether you most need to avoid false positives or false ne

You really would also want to have some sort of loss function, or at the very least a general idea of whether you most need to avoid false positives or false negatives. If it was most important to avoid incorrectly saying it's NOT a P&D, then this is not good performance. If you need it to nearly always avoid saying something which is not a P&D (and thus might be a great investment opportunity), but given that you want to avoid as many as you can, 50% might be good.