Does anyone know if and how much the saddle height has to change (up or down?) when switching from Speedplay Zero pedals to the new Dura Ace SPD-SL?
I think you just need to measure the angle at your knee and be sure it is around 25 - 30 degrees once you have your new pedals on.
It might just be simpler to clip your shoes into the pedals and take a reference measurement. Then switch pedals and cleats and adjust saddle height to match.