You could surely test out setting the PortraitMode key - not knowing the exact values...I'd assume it's just a true/false bit flag. So 0 = false and 1 = true.
I followed exact registry changes and after restarting, there is still not an option to reorient into portrait mode. the shortcut keys also don't work. So I'm ready to throw in the towel on this now. Thanks for your help regardless