I have been shooting 6x7 with an old Calumet 4x5 view camera with a roll film back. I love the format but the equipment is too old, fragile and heavy to do any serious back packing. So I am considering the purchase of a used RB67. Yeah I know an RB67 is not exactly light and small but they seem more rugged than a 4x5 view camera. Is there any known problems I should look out for before I invest? Is an old work horse likely to have shutter, bellows or other common problems?