The crackle shawl in Season 7 Episode 6 was woven at 24 epi and ppi, as it was woven without tabbies, just as a twill. A more open sett would not have worked, as there are lots and lots of three-end floats, just like in twill. The shawl you saw was woven with three colours, but could have been woven in two, an alternating light and dark in each the warp and the weft, with a warp of 2.5 - 2.75 yards. Anything longer than that and I would have run out of weft yarn. It was so much fun to design, starting with a 2/2 twill profile then changing it to crackle manually in my weaving software, so as to be sure that the incidentals were in the correct places.