It's interior pressure
43WM does the same thing. I added weather stripping, which just produced a whistling noise. When the canopy is in the "extended" position (visible gap) there's a LOT of flow out through the gap-- if you're wearing a long-sleve shirt it will suck the material out through the gap. I think it's a combination of low pressure on the outside of the canopy (curved shape) and high pressure inside (Cabin air scoops). If you close that gap completely the air WILL find someplace else to exit. I think this winter with the scoops closed it won't be as much of a problem-- we'll see.
Wayne 120241/143WM