When you install the downgrader .pup from the XMB update you will be on a "hybrid" CFW3.55 that shows 4.30 in system setting but will successfully run toggle qa. Then you can check the qa flag is set by doing the L1 L2 L3 R1 R2 down on dpad and install Rogero 3.7 via recovery menu
See full instructions here:
http://www.tortuga-cove.com/forums/v...p?f=127&t=3708