I’m aware of several folks who have trained bipolar one-channel montages just below O1 and O2, at the top edge of the inion ridge, for balance and gait issues (certainly cerebellar issues) and claim to have gotten very good results.  They used a bipolar and inhibited 4-7 Hz while very mildly reinforcing 15-18 Hz activity. The EEG amplitudes are very small at this location in comparison with other places on the scalp, and the thresholds for reinforcement are adjusted accordingly […]