Prevent overview zoom

How to prevent zooming the view during a drag within in a GoOverview please? Note that we don’t wish to disable panning via drag, nor do we wish to prevent zooming the view by other means such as menu selection. Thanks!
Oh, also, what is the name of Go hint 220 please?

I haven’t tried this, but I would think you could remove the zooming tool from your instance of GoOverview:
anOverview.ReplaceMouseTool(typeof(GoToolZooming), null)

I forgot to mention that there is a table of change hints (< 1000) in the API reference compiled help file under GoDocument.RaiseChanged, and a table of change sub-hints (> 1000) under GoObject.Changed.