Forcing a certain sub-pixel ordering

[Nikolaus Waxweiler]

Hi,
I have a 'Medion MD30219 PH' LCD screen connected to a GeForce4 card 
('nvidia' driver, version 8178) over DVI (FreeBSD 6.0, Xorg 6.9.0). 
I'm trying to enable sub-pixel rendering of fonts. However, Xorg 
doesn't detect the sub-pixel ordering by itself, so, is there any way 
to set it manually without hacking the source-code? If not, which 
files/module do I need to modify?