portrait upside-down (iOS)

[Ben Rubinstein]

Attempting to support portrait upside-down on iOS (specifically iPad); I've 
set the allowed orientations to portrait and portrait upside-down. Rotating 
the iPad has no effect. Tracking the orientationChanged message reports 
landscape left and right, but only "unknown" for the two portrait orientations.

Am I doing something wrong? Does anyone else have this working?

TIA,

Ben