I do have some information on it:

57mm spreader rake, 810mm spreader width, 39 tension on the diamond wire, measured with "classic" Loose gauge, model A.

This is for an Alter cup blade, so aluminium mast and Glaser sails.

I thought Matt sails with 64mm spreader rake, 840mm width and also 39-40 tension.
I wanted a little less prebent, because we're a bit heavier.

To be honest, i hardly ever change my diamond settings. Just by applying enough mainsheet tension the sail becomes pretty flat if needed. Cunningham will also help a bit.

Geert