I have over a thousand hours on aerobatics ~+5 - 6, -2 and my headset (DC) has never moved (maybe I have a big head).
I find placement of the headset leads important, slip it under your shoulder harness and leave about 10cm excess otherwise if you turn your head too quickly it will yank your headset right off and that kind of distraction is something you don't need when you are learning aero's.
Good luck, the aero's really improve your handling skills and your ability to read the aircraft.
XG