I used to BACK our 28' Class C (widebody) through a 10' door all the time (and the driveway was downhill and twisty). I would back up until the mirrors almost touched the door frame; then I'd fold them in. Once clear of the door frame, I'd open the driver's side mirror again, and finish backing in. Yes, it's hard to see inside the building compared to the bright outdoors light, so I added reflectors on the driver's side polebarn posts at the right height to be illuminated by the taillights. You just need to be patient is all.