This looks like the making of an article on the subject (hint).
Could you elaborate on the secondary application of power in the single? One thing I've found is that my "old slow rod" will cast a single better than my "new fast rod". My feeling is that because the faster graphite will try and straighten itself out faster constant application of power is more important to "keep the rod loaded". I've attempted a "two-phase" cast before, adding power once the grip has left the water, but have not been successful in directing that power in a place that leads to a successful forward stroke.