If the seal on top of the slideout is good, you should not have a problem. Just make sure you have all the leaves, sticks and debris off the top of the slide out before you retract it. That is standard practice for those who do not have a slide-out topper.
'07 Winnebago Journey 34H, ISB-02, MH2500
Toad - '08 Ford Taurus X
Blue Ox, Aventa
US Gear UBS