Hello,
During installation, the rear flap and beading have to be pulled down far enough so the top willl tuck down tight against the body of the car. As this is being done the top is also stretched toward the side windows from the center of the bottom bow, so you don't get those funny little corner wrinkles near the door/top/window corner area. The back bottom bow flap and beading area of the top can also be re-stretched and re-glued in the in the future, without too much difficulty, if wrinkles or flips occur after installation. Naturally making sure the flap is not flipped up when you put the top down will help also.