:) Sorry. Don't know anything about a 4th form in the WingChun fist non-weapon routine. It's common knowledge that Master Ip Man taught a more diverse regimen to his first students in Foshan (Mainland) before teaching in Hong Kong. (under duress). From what I can see, he did streamline his Hong Kong style to NOT include techniques from other Southern styles that had been incorporated early on (Red Boat Opera performers of various style affiliations). * Reading the notes from the last vid you posted, I see from the comments section that Master Ip Man's son, Ip Ching created the form as a compilation (essence) of the WingChun non-weapon forms (3).