Frenchs Forest to Nth Ryde

I would like to start riding from home (Frenchs Forest) to work (Nth Ryde) and am looking for an interesting (ie dirt) way of doing it.

I can cut through Cascades and come out at St Ives, however I'm then left with road the rest of the way to Nth Ryde.
Does anyone know of any way of linking up with Lane Cove NP? I've been looking on Google Earth and thinking perhaps from Davidson to East Killara then across the highway to somewhere behind Gordon?
Am I doing this the hard way?

Does anyone already do this sort of trip?

Or will the forces of evil get me and force me into road riding...

cheers
Loki