I know my son used one when he moved from Golden to Albany last year. I didn't see any scratches relating to this bag on the roof of his car when I visited him last month, but then I didn't really look so all I can say is the bag didn't gouge the car's paint.
After seeing that 2011 Cruze with hail damage, don't thing I would put anything on the roof. But would guess it depends on what he is planning on putting in that bag. Would think fiberglass insulation, foam, or bubble wrap would be okay.
Daughter got roof racks for her Kia Soul in that black vinyl strip, had plugs on it where you could bolt down roof racks from etrailer.com, looked for those on my Cruze, couldn't find those, but do make racks for the Cruze. She wants to carry a kayak up there, but anything we looked at, even with way expensive stuff, still need front an rear tie downs. Where in the hail are towing hooks? Just paper thin plastic all over the front and rear of that thing, just like the Cruze.