Visited with Bob Davis (Zona) couple weeks ago in Peoria, AZ..
He is still diligently pursuing several projects/ideas, although no longer building tandems. Bob's a great guy and forever tinkering.
Let's hope his health issues improve.
Pedal on TWOgether!
Rudy and Kay/zonatandem

(Attached a photo of Bob and his wife taken a few years back on one of his prototypes.)