While I have never had a camper with a slide out, my neighbor does and said he was told by the dealer rep on his walk through to slightly tilt the camper downward on the slide out side and this will allow water to run off the side of the camper and keep water seepage into the camper at a minimum. Neighbor said he has had no leaks in five years. Yearly maintenance on the slide out would be must. Good Luck.
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