I like the Crybaby circuit, but inductors have such a wide tolerance that a few of the component values need to be fine-tuned by ear to get the most vocal sound.
Here's what I did to mine:
1. I replaced the bjt input buffer with a darlington, which eliminated the need for a true bypass mod.
2. I replaced the sweep cap with a larger value to get a more vocal wah sound
3. I added a second, much larger, sweep cap on a switch for a very deep wah. Sounds good on bass and on guitar.
4. Upped the input cap for both the input buffer and the main wah circuit
5. Increased both the Q resistor and the bass-treble transition resistor for a more vocal wah with a smooth transition from bass to treble.
If you're interested I can post my notes from when I made the changes, but remember I didn't rebuild a new circuit from scratch, I just made some mods to the existing circuit board. Also, the specific values I chose were by ear, so to optimize yours, you might end up with different values than I did.
Here are some resources I used at the time: