I am not an authority at all but I have a little knowledge. First I wonder if your fabric is a proper tartan. It might be one of the many unofficial tartans. I am, for example, sitting with a pillow at my back from one of the great American wool houses. The tartan seems to be a correct rendition of one of the Black Stewart tartans but the size of the pattern may not be correct. The size of the sett from one of the authorized weavers may be different. Just a thought. I admire your dedication and generosity. Keep it up. I saw some interesting fabric pleated to the pattern in various photos and at Loon Mountain this year. It is an art in itself.