Thanks! I didn't do anything special to tension the cords - just did it by feel. I had the experience of one other chair to draw on, except that one was done with paracord instead of Danish cord. I make the warp cords tight enough that there's no noticeable droop, but not super tight. You can't really make them super tight anyway - if you try, the cow hitch will start pulling the pair of cords down and away from the rail. Any slack will tighten-up as I do the weft weaving.
