Barry,
I have found that the way to eliminate first-filght-nerves is to either make the plane too light to damage itself, or so low in investment you don't care a hoot
Then they all fly.
Similarly if you develop your sail plan (probably in cardboard) and cut a trial suit from available material it will take a very short time and give you freedom to learn about the fittings, rig, sheeting without worry about stitching, footropes and getting the cringles (nasty, that)
I see that Swan has ochre sails - fortunately the free swatches of trial sail material come in a variety of browns and reds, or can be persuaded that way.
The trial triangles may be obtained at this time of year from any seaside bin. Often in a choice of colour and size, but please try to avoid any umbrella advertising Martini uness you want this shade of green!
Pic attached of templates for my Footy (Razor) sails and a selection of free swatches
Better scale sails from drafting linen, well washed to remove the size the other natural materials that you are being pointed towards.
The Thames Barge model experts in AMBO tend, I think to dye their natural sails in brown dylon then adjust by arcane methods involving cold beverages and prayer
BTW, I have sailed a Thames Barge with newly dressed sails.
Colourful. Very. For weeks.