Remember, spellcraft is a cross-class skill for all true dragons except for the blue. This means that in order to qualify for Permanent Emanation, a dragon would have to have something like 50 points put into spellcraft and have HD 47. Since the accepted strategy is essentially to have a permanent antimagic field emanating from the dragon and then melee, the only reason CL comes into play is trying to make sure the Wiz doesn't escape by telporting or dimension dooring or something of that nature. Mmmm... maybe dimension anchor or something like that...