Thanks. This is basically what I ended up doing except I used 2 45s for each 90 (top and bottom) and then connected the two with a straight. Used #8zip screws to secure, metal tape, mastic and then covered with foil backed fiberglass. I used R-38 12in batts in the cavity and on top.
Future project, fix the crap insulation job in the attic. Wood shaving insulation under the floorboards and fairly thin batts on TOP of the boards *sigh*. When we get the roof redone in a couple years I plan to bring the finished attic into the thermal envelope proper.