Daf Yomi - Sukkah 24 - Canvas

When one uses a canvas Sukkah, there is a concern that the walls will flap in the wind and this will invalidate the walls. The Poskim suggest that one can tie ropes or reeds from one side of the Sukkah to the other. The ropes or reeds must be within three tefachim of each other, thus applying the principle of lavud, and this would obviate the need for the canvas walls. The Chazon Ish rules that the walls cannot sway more than three tefachim. One must wonder if this means that the walls cannot sway three tefachim in each direction or does it mean that the walls cannot sway three tefachim entirely.
I did notice an interesting discussion here and it continues here and concludes here.