Finally, Some CF Bling for the Tandem
I've had the stoker's Garmin mounted to the top tube, but I saw this cool gadget on our very own bdop's site called the dashboard genie. He very kindly provided some measurements so I could be sure it would work on the tandem mounted backwards. The tube is CF and I think adding this to the bike made it 3 lbs lighter.
Nicely mounted Garmin and out of the way of the stoker's knees!
Gear Combo Guru
I've achieved a similar position for the stoker's computer by using a simple plastic extension that is designed for mounting a computer on aerobars:
It might not be carbon, but I think it weighs even less than your bracket and carbon bar combination.
But not 3# less than the OP original configuration. The amorphous carbon device Chris uses
is 0.1 on the bling scale.