I'm working my way through the collection of Coptic bonnets in the collection of the Krefeld Textile Museum. Number 12729 is an interesting one. It features a couple of twined motifs. Interesting to me was what happened with the shape. It began as a 34 inch long warp. Getting to the middle I was thinking that my replica would be tall and thin, not the short squat shape of the original.
Then I put in the chain line, which appears a few rows below the initial edge loops on the front. The chain line seemed to make the hat want to be wider. I sewed up the side seams, and blocked the hat to satisfy that chain line ... and voila, the same proportions as the original!