No you can't retract with slide out.
The roller has a retracting spring, always under pressure; trying to roll up; to keep the cover tight. When the slide retracts, the spring and roller takes up the slack; opposite with extending the slide.
There is substantial spring pressure.
If driving 70 on the Interstate into a crosswind isn't supposed to be an issue; it stands to reason that a normal wind shouldn't be an issue.
Unlike a huge awning these slide covers are tiny in comparison; much less surface area, tiedowns are essentially the trailer itself, and the only place wind has to get under it is from the small gaps at the sides.
The deflector isn't a separate piece, rather the bottom of the structure that holds the roller in place; designed in a way that it (almost) fills the gap between roller and slide room wall. It is essentially the bottom of the case; the option that I didn't get, but should have.
I'll take a photo and post it later. Worth a thousand words, as they say.
XLR Hyperlite 29HFS
Ram 2500 6.7L CTD
A Modder's work is never done!