the trick for making a bend like that really is the pvc bendit tool that is mentioned lower down on this page. if you were to use a b series bender with a 4" sleeve, you could completely and evenly heat the pipe from end to end, and if you used a second 4" sleeve, you could make the bend without having to worry about the pipe wall collapsing.
that is definitely the best way to evenly heat pvc pipe for bending. i noticed that there is a link to the site down below, but it's got the url wrong, so it doesn't work. the url is http://www.pvcbendit.com and the page he was sending you to was the PVC Bendit Gallery
It really is a cool tool, and it works great.
