If you set the temperament to "flat" but then modify the unison width, is the temperament still flat?  Or does the "flat" setting lock the unison width at zero?  Or maybe neither is true and I don't understand any of this.  Help!

Bill

Yes it remains flat, that is, the mean values for each unison build a flat temperament. Besides, the beatings that you still hear with a large unison width under flat temperament prove that the flat setting does not lock the unison width to zero.

Bill