Is this for a LiveCD or an install?

For a LiveCD, you can try: knoppix xmodule=vesa screen=1400x1050

We run a remastered Knoppix with limited screen rez options, so I couldn't test this. It did prompt me to grab some ISO's for "normal" Knoppix to play around with.

I should have 6.01 VM'd soon and then i'll try the above code myself too.