We only have a slide in the living room and if aligned with the wind just right, it can flap some. Bedroom is on the other end so never been bothered by it. I've often wondered about a small inflatable kids swim ring to stuff under it, and stored deflated, just to minimize the flap.
I'd say get the cover, far better than the debris that you get without one.
"I might be movin' to Montana soon..."
2013 Eagle 29.5RKS
2013 Ford 6.7L diesel F350