I agree that the brief film clip which I believe comes from the Hollywood film would indicate that Uncle Dave was not playing all the notes while turning the banjo in a circle. However I do reccommend that you take a look at the Cordell Kemp clip to show what can be done and surely Leroy proves the point.

Sadly this appears to be the only piece pf film of Uncle Dave performing as it is the only clip that ever shows up.

Hoot