For anyone who's interested, I've just discovered YLI button hole silk thread on line at joggles.com. They have an incredible assortment of colours.
Knotty, can you tell me what size this thread is? I've used Gudebrod silk thread in sizes D (.305mm/.012") & E (.325mm/.0128?) and Griffin silk cord in sizes 0 (0.30mm/.012") & 1 (0.35mm/.014"). Recently, I've tried a variety of synthetics and I'm quite happy with the results, but I'd like to give your silk a try, as you're so pleased with YLI, and it comes in so many gorgeous colours. My only concern is that I use a double thread method, and it may be too thick.