Lokescotty, please post pics of this install as I want to do the same to my wobbling bike!
You might want to wait to find out if it works for him.
Steering dampers are popular on sportbikes because they have very little rake leading to marginally stable steering i.e. they change direction very easily. Often, setting down the front tire after accelerating can lead to some headshake in that type of machine.
Choppers are on the other end of the spectrum. They have huge rake and are usually stable as a tanker in a straight line. Their problem is that it takes too much input to change direction at speed.
I suspect he is suffering from a different problem causing his wobble. Maybe the damper will mask it, but I'd wait for his results.
Choppers are not exactly a high speed bikes yannow. Might wanna check the speed rating on that front tire.
Harley tourers were famous for speed wobbles. People sell braces for their frames that fix that. Doubt that a steering head damper would made any difference. In 2009, Harley got around to fixing the frame.
If this is any indication, your Hammer should be stable as hell at speed: