They can be cut down. You will need to remove the roller from the arms, and remove the rear insert, and remove the awning fabric. Then you can use either a chop saw or sawzall to cut the excess length from the tube. Cut the same amount from the awning fabric, and sew it back so it doesn't unravel.
You can move the mounts, slide the awning fabric back in place, and reinstall the rear insert.
Can you tell I've done this before?
