I just love those old Vox Clyde McCoy's and Cry Baby's, nothing beats them. The only trouble is that they cut a lot of your tone when you switch them off. You can use a buffer pedal before the wah in order to prevent the loss but that makes the wah sound too brite when you switch it on again. Some newer Dunlop wah's have a built-in buffer and suffer from the same aggressive brite effect. If you put the buffer after the wah it's no use, your high's are gone.
So, what's to be done? Well, the problem arises because the input impedance is intentionally low in order to obtain a better wah effect with more tone. The bypass switch, however, only switches the ouptut of the pedal. The low impedence input of the wah is never switched at all and stays connected to your guitar signal all the time, even if you bypass the wah effect. The best solution, therefore, is to replace the bypass switch with a DPDT switch and rewire the pedal for full bypass of both input and output. Then use a buffer pedal after the wah in your chain of effects.
This way there will be no alteration of the wah effect when you use it, and no coloration of your sound when you switch it off.