Have ridden a bamboo Calfee single; every bit as comfortable as a Calfee carbon fiber.
Have hefted/seen Paketa tandem at Interbike a few years ago, but not ridden one; so have no comparison experience.
As far as overseas mass production goes for c/f or mg tandems, it is just too small of a market niche for them to spend the $$$ necessary.
C/f tandems are quite labor intensive, but then you get what you pay for.
We do ride a custom c/f Zona tandem and just celebrated our 25,000th mile on in 2009. Still extremely pleased with it! Quality lasts . . .
Pedal on TWOgether!
Rudy and Kay/zonatandem