The GUI doesn't automatically boost the voltage (and I'm not sure the current version of the modules does either) - dial it into the voltage you want and set it to that.

Note that you should make sure to set the voltage to the absolute lowest stable value for the clock speed you want. High voltages cause electromigration in the chip (= shorter device lifetime), high heat output (= overly toasty phone), and high power consumption (= low battery life). You'll need to incrementally lower the voltage and run a stress test until it starts crashing, at which point it should be raised to the last stable value.