Found this paper on my computer. It might encourage more flyback converter experiments. Since magnetic propagation time is an important factor, means for slowing the magnetic propagation from one coil to the other could be useful. I did some work on slowing down the magnetic propagation across a ring core with interesting results. For propagation along a ferromagnetic rod it is possible to slow that down by a series of coiils or single turn loops each shorted by a capacitor. In effect you create a magnetic delay line. Maybe this could be used to effect here.
Here is a paper on magnetic delay lines showing how we can obtain significant time delay in the magnetic domain. I have another paper on the transformer I built, I'll dig that out next.