For me it wasn't the actual water, but rather the 4" of frozen snow/ice that I had to wait to melt enough to shove it off the slide roof. But that was back in the early 90's. Water may be directed away from the seal, just tilt the RV a few degrees the direction you want water to flow.
Since DW is unable to travel much, I think you guys talked me into buying the sun-shield material too, if the OEM Carefree material goes South without me.