Correct position of Topper for Slides when closed.

If installed correctly, the rail on the body should be high enough to create a fairly decent slope to the fabric. On my 2 slideout awnings, they have about a 30 degree slope. There should never be any pooling on a closed slide cover.

If yours is almost flat, the rail is too low and should be re-positioned higher. If only a slight slope, and the screws are on the top of the rail, you could remove and turn over so the screws are under the awning. That would give you about another inch of slope height.