Overscan adjustment?

[Asxetos]

Anyone knows how to adjust the HDMI "overscan" on an Amlogic box (Prometheus)?
My TV has 3 settings, but even on the smallest one the statusbar and menus are half visible on Android UI.

We can adjust the screen on XBMC just fine, but a global setting would be nice. Perhaps a change in build.prop?

PS tried this setting (found on the net)

persist.sys.hdmi_resize_x=xxx (tried 3-10)
persist.sys.hdmi_resize_y=yyy (tried 3-10)

Does NOT work...

[cde]

Use the SettingsMbox app? It allows scaling from 100 to 80%. I use hdmi and my tv needs about 88% to show the notification bar completely as well as both edges of the screen.