Fit2BKilted I think that it best you think of it as a "design constraint" rather objecting to it as a limitiation.
But Nick really does have a fair point, most weavers wouldn't entertain an odd threadcount, I suspect they would be likely to question it ( if not double it up themselves!!)
The point about doubling up the thread count is a good one, but I know you still won't be able to get you dashed lines....