Richard,
I cannot tell accurately how much the centre of pressure, CP, in the sail moves when going from flat to cambered. My half-informed guess from the work on Malena, back in 1994, is that the CP may move 2-5% of the wl. forward.
Actually, Malena is the only boat I have owned with both a flat junksail, and then 3-4 with camber. The first version with camber (NL 24) was made with hinged battens added to the original sail. Since the aerofoil of that sail was symmetric, the weather helm increased (moderately) compared to with flat sail (and with the BR). This led me to assume that the CP moves back and forth with the max camber point of the sail (generally speaking). However, the CP moves around quite dynamically during sailing. It moves forward with decreasing angle of attack, AOA. As we bear away without easing the sheet, the AOA is increased and the CP moves aft, with increased weather helm as a result. This is actually quite helpful in making a boat keep the course in steady winds, with the tiller locked. This movement of the CP is much stronger in a flat sail than in a cambered one. I guess you have experienced, just as I did, that it can be difficult to tack because the sail gives such a strong lee helm as you head up.
Making the sail.
Making a sail with camber cannot be said to be experimental these days. I therefore suggest you save time and head-scratching and just sew a new sail using the quick amateur method B on assembling the panels. No need for re-inventing the wheel. You have plenty of other odd jobs waiting: Get that outboard engine out of the water, and possibly improve the rudder, or build a new one later.
So just hurry up and build that new sail - that is plain sailing.
Arne