If you have a 500K pot, and want it to sopund like a 250K pot, solder a 1/4 watt 470K resistor to the outside lugs of the voulme pot.
Rick....did you find that messing a bit with the pot taper? it does change it some.
Sorry. I must have misunderstood your original question. I thought you were asking how to make the vol control act as a volume and tone control in one pot.