After some experimentation, I’ve decided to use perle cotton for the trim. The wool was nice and black, but didn’t show the braiding very well. The linen showed the braiding beautifully, but was more gray than black. I just couldn’t afford to do it in silk.
The braid pattern I’m using is “A Broad Lace of 5 Loops” from Tak V Bowes Departed.
I was going to add a photo, but I just can’t get any detail from the black thread.