Thanks to all of you, Mark I've been through most of the links in your sig - Thanks loads!
I'm going to try to estimate the static and dynamic head of my proposed system. I've emailed Hayward asking for pump curves for the 1 and 1.5 HP Power flow Matrix AG 2 speed pumps. Haven't heard back yet. It seems to me that the sweet spot would be a two speed pump with enough head on high to prime the solar and enough head on low to maintain the solar's flow rating (accounting for system dynamic head and psi required for vacuum check valve) and turn over the pool in eight hours (without the solar). Clearly this could all be achieved with a variable speed pump of sufficient capacity but those critters are pricey.
Does anyone knoe of a solar control system that will start a pump and run it on high to prime the panels and then on low (after staic head is returned).