reduce frequency of a crystal oscillator - FV-1

so I've made a few FV-1 pedals, and for my next one, I want to be able to fiddle with the clock speed. taking the basic schematic from the datasheet, my idea was to put a pot at one leg of the crystal, the 15pF cap to ground on the wiper, and the third leg of the pot also to ground.

it will be a few weeks before I can actually test this (in the middle of a move) but I'm curious if this would work or if there's a better way to do this.

Thanks!