RE: Could I Put Monokote in my HUGE gaps to lower flutter or eliminate it??
I would not fly a plane in that condition. Cut out the hinges, use and exacto to route out new hinge slots. If the Stab itself is that far off, then rebuild it to plans. If it is an ARF, send it back to the mfg for a replacement.
Any hinge gap over 1/8, and especially a gap that varies from one end of a surface to the other tells me that the symmetry is way off and likey to be a highly unstable / erratic flyer.
Do it right.
DP