Extra dimming the backlight?

[New Daddy]

Can you dim the backlight even further than the default "dim" level of WM 6.5? I need to conserve battery as much as possible as I'm using my TP2 as a GPS tracker and it consumes a lot of power.

With my old HTC XV-6700, you could almost black out (and switch back on) the backlight by long-pressing the power button, but this doesn't seem to be part of TP2's feature. Any way (registry edit perhaps?) to further lower the dim level during idling?