I didn't even think about fabric fitting both the window frame and the upper door frame. I'm sure both door frames are the same all around the edges but how or why one works with the sliders may be quite different.
I did just check my son's sliders on his YJ and it looks like the door frame has a couple of pieces of metal that raise up to support the bottom of the slider frame. Maybe what is supporting that is the same metal rod that the vinyl windows fold over when unzipped. While walking back in the house, it dawned on me that if he wanted new fabric, which he really does need, I'd have him call the brand that makes his top and see if the vinyl window fabric will fit on his existing frames. They may even know about the actual slider windows fitting, or may still sell the fabric, if they are the same brand.