I know you can alter the frequency range of your wah (not the amount of sweep, but where in the frequency you can sweep) by opening the thing up and moving the straight plastic piece with teeth attached to the top of the pedal to a different section of the gear that moves the potentiometer. That probably is a confusing way to say it, but that's the best I can come up with (still on my first coffee of the day).

I'll bet Lordathastrings has already heard of this and done it and can explain it better than I just did.