As my understanding goes as soon as you fly over the cdf as long as you have started the turn (ie you are remaining within the protected zone).
However please don't quote me on this I'm probably wrong. (no doubt will be corrected quickly enough.) If you are only at 3000' however I'd be in no rush and would rather concentrate on rolling out on correct heading in correct place than thinking about desceding (fair enough if your high but why complicate things?)
C99