So have not covered fifth wheel yet, and had lots of rain, carpet on left side of slideout felt damp, then we got hit with heavy rain and now hand comes up wet on only that one side, I thought seal looked good on our 2004 wilderness lite, but maybe it comes in from around the moulding on it. Gonna try figure it out, but will hope to get it covered soon as we are supposed to get some sun soon.
OK, I would climb up and look at the outer molding closely where it makes the 90 degree angle. I had one that had a big crack/opening where the vertical met the horizontal at the top corner. After sealing that up my damp carpet along the edge of the slide went away.
On my last one I found that problem stemmed from the mounding on the roof of the slide. BTW did you mention what position the slide was in, I assume out?