no, shrinker/ stretchers dont make 90 degree bends, least not in one clamp. they give you a gradual bend. i have the mittler brothers air powered unit. its a nice unit but i haven't really got to use it to much yet. my only doubt is its ability to do what i want with the air power. very soon i will be putting it to the test and putting some good air pressure to it and see how it does. if i were you id get a shrinker/stretcher unit that is foot powered. that way you have both hands to hold work piece. hence the reason i bought the air powered version.
Marc