You can do the measurement tricks but I'd start with your spreaders 50mm aft of the mast track as noted in the Nacra Infusion setup guide (yes I know it's a Inter 18 mast that is likely carbon, I don't have numbers for those). You want your diamonds cranked close to 43 on the Loos gauge if you're in big breeze.

Finally you might want to talk to your sail maker some about the measurements of luff curve.