My Corsa suffered some minor roof damage from the hailstorm. The hailstones were a maximum of about 2 cm in size. Cars parked next to my Corsa (Citroen C3, Hyundai Ceed and similar) didn't get dented. That's why I think the sheet metal on the roof is too tinny. Have you experienced a hailstorm?
Google translated to German, sorry :)then an MTB shouldn't be a problem either.
I have ordered my Corsa and now waititng for it: /
Manual tell that length of load compartment with folded second row is 1385. My MTB bike from bars to rear axle measure 1300. Maybe will need to pull drailerur to front. But height of folded seat to roof is that I am worried, I need 82cm minimum (bar to top of fork)