Just finished such a solution for my pop-up (4WheelCamper) I was lucky. 4Wheel comes with 2' wide strip of 'soft' velcro where vinyl meets the roof. Full length of sides.
Used 24" reflectix cut in 42" pieces for ease of handling [3 / side]. Covered 1 side with Buffalo plaid flannel [sewn to reflectix] Sewed strips of 'cat paw' velcro to upper edge of shiney side. Seems to hang well. Also feel will help keep heat down during HOT summer days. only a couple of minutes to hang. NO Sadly they must be removed to lower roof.
TakeCare ~ TravelSafe ~ HaveFun
PM me any ? ~~ Got pics can't stick 'em here.