This forum actually inspired me to get one, and I (and the family) love it. We'd love an Adventure Island Tandem, but don't want to buy something big enough to tow it or try to store the beastie.
We are a mini cooper family
So yes, your i14t tandem PLUS sail, pedals, seat, pump, paddles, and lifejackets can fit in the back of a Mini Cooper Clubman. People stare at the clown car with it's huge magic boat.
If I have the kid with us, the i14t is light enough to put on an aftermarket roof rack and all 3 can go. Love this thing!
Paddles fast, peddles super fast, and the sail probably doesn't add nearly as much speed but it keeps you going during resting and is fun to play with. We paced the motorboats in the no wake zone, and blew the standard kayaks away. The peddles pop in and out very quickly for when you're going over seaweed or beaching to switch spots.
Honestly, it is so fast we are thinking of pulling the 3rd person behind us on an inner tube (or our cheap Coleman inflatable... glorified pool toy, but hey)
To new buyers - yes get at least one turbo fin set and the sailing rudder. You will still occasionaly get some wind pulling you around but it now rarely an issue.