I unzip my HW27SC and it makes folding in the canvas easier. I put pull strings on the zippers that makes it a lot easier to use and do not unzip all the way, about three inches from the top. Easier that trying to connect the zippers at the top everytime.
2009 Flagstaff HW27SC (NTU 2014)
1999 Ford F150
I have always unzipped the canvas to about 1" from the top. Not sure why other than when I first watched how to pop up a pop up, they went around and zipped it up. Seemed logical that it started unzipped if they zipped it up to set it up. I do think it aids in laying the canvas flat so as to lessen bunched up parts and allows the top to close properly.