Zach, before comitting to the wah build, I tried a few different pot values, and 10k chopped off the extremes of the sweep. 20k worked best.
I got one of these Superswell wah pots, as well as the yellow rubber top plates, and feet from Das Musikding in Germany.
http://www.musikding.de/Superswell-pot-20kMy son just wanted it to look esily identifiable from his Crybaby on a dark stage, hence the flourescent yellow and green paint!
The Terry Wogan / Terror Wahgwan bit was all his idea.