Quickly review משנה ברורה ס’ שס”ב ס”ק סו which discusses a machlokes whether the top crossbeam/ string needs to be taught so it will not sway in the wind.
https://hebrewbooks.org/pdfpager.aspx?req=60389&st=&pgnum=55
Why do the יש מחמירים disqualify a צורת הפתח which the top string sways in the wind?
According to the יש מחמירים how much swaying is acceptable?
The Mishna Berurah brings the opinion of the מחצית השקל that is based on a phenomenal chidush in what creates the mechitza of a צורת הפתח
Learn the חזון איש או”ח ס’ ע”ז ס”ק ו (in the back of some prints of the Mishna Berurah)
https://hebrewbooks.org/pdfpager.aspx?req=14336&st=&pgnum=238
According to the חזון איש when is the top string swaying an issue and why?
Other opinions on amount of swaying in the wind.
See ערוך השולחן או”ח ס’ שס”ב סע’ לז
https://hebrewbooks.org/pdfpager.aspx?req=9101&st=&pgnum=429
See אג”מ או”ח ח”ה ס’ מ אות ב (in middle)
https://hebrewbooks.org/pdfpager.aspx?req=922&st=&pgnum=176
See אמרי יושר ח”ב ס’ קל”ג
https://hebrewbooks.org/pdfpager.aspx?req=609&st=&pgnum=397&hilite=
Learn גמרא דף יא: “אשכחיה רב ששת (seven lines before the Mishna) until the Mishna
Clarify what the concept of חוקקין להשלים and what the machlokes is.