G'day Fright
It's quite common for the kit's sails to be quite thick.
What I did on my AL's Endeavour when i did the sails, was to use our old 1000 lines sheets. They were a very pale sandstone colour. At 1:64 scale that 1000 line sheets was equal to about 16 lines which is very close to the canvas that was used on the original ship.
I then stained the sheets with instant coffee in a patchy way. I used CA GLUE at the edges of the sail to stop the threads running, AFTER I drawn up all the stitching lines on my computer and printed Both side of the sails on iron transfer materials making sure that they registered correctly.
The result was very good, and no one knew that they weren't sewn. Also the the lines were very thin. The coffee stains made the sails a weathered look.
Unfortunately, we moved home last year and in the process the model was damaged quite a lot, and has been packed away for repairs after I have finished my current build. It's too hard to get to it now. Another disturbing point is that all of my digital photos are somehow corrupted. I'm hoping it that I'll be able to retrieve them soon.
So I can't give you any pictorial images to show you.
Havagooday
Greg