Slide Out Topper Problems

I purchased some Dometic Deluxe slide out toppers for my Cedar Creek 5th Wheel trailer last Fall. Having camped with the trailer in the rain a couple of times now, I find that they collect water! This is a real pain as they hold and dump a lot of water when the slides are put in. Of course, this also means that the slides are put up wet to mildew. I called the Camping World that installed these and was told that there was nothing they could do. They even told me that these were not for use for rain! What a crock! Does anyone know of a way to fix this problem? It seems like most every camper that I know has slide toppers and they all work fine except for mine. :(