The best tool for this job is a shrinker/ strecher a couple of companys make them there not cheap but its the best tool for making the contours you can bend a 1" 90 degree in some sheetmetal and by shrinking or strechting you can make almost any dog leg or window channel its on of my most used tools in my shop. Eastwood sells them and probably has books or info or google ron covell he's the best and sells tools and has books etc.
www.covell.biz