I drew up a little Kingway copy in CAD here's an image:

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This is Wes Johnson's which I ripped off - https://www.youtube.com/watch?v=FjYeiJ1q-Tk

He uses ground bar is this really necessary? I was thinking why not just mild steel or aluminium for the whole thing.
Aluminium would seem a lot easier to make.
Drill bushes I understand as they are contact points.
I think also for the circular ball that goes into a 45 degree cone just loctite'ing the ball the the bar above might be better.

Detail of 'bannana thing':
photo hosting
Dimensions I will probably change.