The papyrus is intact except for that one cutout ---no problema, amigo, it is just a dihedral template.

Because I'm an obsessed nutcase I penciled in some reference lines to create a proper centerline, etc.

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Just below the elevator link you can see the C/L running all the way aft.

One option is to cut down a 48" L.E.G. wing panel that I happened to have on hand. So here I've drawn a cut line that would work out well I think.