using lavud to kasher the walls of a canvas succah

Question

I am learning meseches succah be'iyun right now, and on Friday my rebbe gives a short halacha le'maaseh chabura on the sugyas we learned during the week. In last week's session we learned some of סי' תר"ל . In the first Magen Avraham there he states that if you are creating a wall(s) with לבודyou need to have 4 walls. In other words, the leniency of 3 walls only applies to real walls, but if you have a מחיצה גרועה this leniency does not apply and you need to have 4 walls. >This means that if you want to be machshir your canvas succah using string and לבוד *you must do this on all 4 walls*. I was wondering what psak many succah manufacturers are relying on in only putting lavud straps on 3 walls, for I checked the websites of a few succah manufacturers and they said to do just that. Thank you so much for your time.