It is still hard to decide..... sorry......
I would go for the smallest / finest with the shortest possible distance of stitches - and the colour should not have too much contrast to the cloth
will you colour somehow the cloth, means some weathering or some more brown (with tea or similar)?
Only that you get a feeling for the final sails, here some images of my sails (which I ordered for my Coureur from a specialist in sailmaking, so these were not made by myself) - unfortunately he is not making any sail sets anymore -
photo made with artificial light - the real are darker
following photos are better showing the real colours
You can avoid the problem of stitching always being out of scale by gluing hems and using a glued thread to mark the seams.
So it is a sketch or impression of a sail rather than a tiny version of the real thing.
Your sail look very nice. Will take your advice on the stitches and tread color, was thinking of tea for staining, is it better to stain before making the sail there not much info .
On other subjects am looking for a trawler kit, comming from finishing village as you can see from photo included
The sails are looking very good - Bravo
Also the size of the installe one seems to be absolutely correct - only check the front end
on Boudriots drawing the edge is fixed to the fore end of the bow sprit