Very tricky. Your going to need a PAL Gamecube to output a Progressive signal via VGA. Give me five mins and I'll look into it.
Does your TFT have component inputs by any chance? I VERY highly doubt your PAL Gamecube will be able to do this. You might need to buy an NTSC one.
EDIT: You can do it. But it is going to be hard. I've found there is NO way the Gamecube can perform a scan conversion.
You'll need an Official Nintendo Component Video cable as the gamecube can output a progressive signal from it's DV port using this. This can then be modified to output a RGB HV via VGAl, but your monitor must support VGA Interlacing at 15Khz. How new is your monitor?
Or you can just buy a VGA box BUT you'd need some VERY expensive cabling and IMHO is not worth the price you'd have to pay.
Edited by Jimmeh_ on 06/09/08 6:05pm