On our custom Zona tandem, measured c to c from pilot's to stoker's seatpost, is 24 1/2". Tip of stoker's saddle to her handlebars is just under 12". Wheelbase is 63 1/2".
Through the decades, Americans have gotten bigger . . . not just in girth, but also in height, so there is a definite need/trend for tandems with longer wheelbase/stoker compartments.
Most unusual tandem we've co-designed is one for pilot at 6'7", stoker 5'3".
No such things as 'one size fits all!
Pedal on TWOgether!
Rudy and Kay/zonatandem