jorbill2or wrote:
Slide toppers should be water proof however it would seem your leak is a seal ( the rubber around the opening) problem! slides WITHOUT toppers at all do not and should not leak! I'd fix or have fixed the slides seals before being concerned about the topper who's primary purpose Ive understood is to keep stuff , branches leaves etc off the slide roof not water , however it does do that.
X2
Find source of leak and then fix it.........slide out seals keep water out not slide toppers.
Then after finding/fixing leak spray your toppers with water-proofing available at most any sporting goods store. Unless they are weathered/worn out..then replace them