Caroline S

I did sew the seams as you suggested and pressed the seams open. I then stitched in the ditch down each seam with a herringbone stitch. The first photo is a closeup of the herringbone stitch. Second photo is of the first three rows done next to the rest of the rows to be sewn on my design wall (aka the curtains in my loft, studio, office, sewing room etc.)

I was concerned a bit about the thickness of the seams but had no problem at all. The biggest challenge was using so many different corduroy fabrics of different weights and wales. Thanks for the suggestions.