possible "hack"? add a capacitor(s) to the GI line(s) as a little more buffer to keep voltage stable?
same strategy done to cars packing extreme stereo's so the headlights dont blink with bass pulse.
if that doesnt do it well enough (for truly retentive!) then hack in a separate-independent power supply (6v wall wart?) to run them and DARE them to even-ever think about flickering again!