So I have been testing the layoutDirection property, as well as direction style property, and have had success using both in NORMAL mode. However, in Fullscreen Mode, the positioning ('x') shifts when I switch to 'rtl' direction.
In NORMAL mode, the switch in directions works fine, no position shifts. In Fullscreen, the UI shifts half off-screen (again, 'x' position shift) when switching the direction to 'rtl'.
Ok, so I noticed that my Application.mxml had a width and height property set.
If I remove these, then it works fine. The shift in position does not occur.