You could spend more on tandem specific bike rack/truck extender than the tandem is worth!
Pop off both wheel (remove seatpost with saddles and stoker bars attached, if necessary). Flop down the rear seats of your vehicle and put tandem inside, either standing up of laying down.
Think outrside of the box!
Have hauled tandem in '60s VW Squareback, 84 Honda Hatchback and now inside a 97 Honda station wagon. Works fine for us.
Quality tandems do keep their resale price and can rack up great mileage.
Have designed/owned 4 custom tandems. Our Assenmacher we rode for 64,000 miles; our Colin Laing for 56,000 miles; our Co-Motion 57,000 miles and our current carbon fiber Zona tandem just rolled over it's 25,000th mile this year. Our first 3 custom tandems were sold for $1,000+, used, with us telling the owners how many miles were on them. We do maintain our own bikes and keep 'em in good condition.
Quality lasts . . .
Pedal on TWOgether!
Rudy and Kay/zonatandem