Car-topping a Tandem Island???

Okay, so I just picked up my Adventure Island yesterday! 2014 demo model from Wind Toys. Very nice people there.

However, a seed of temptation was planted in my brain the second I walked onto their lot: should I go for the Tandem Island?

I drove home safely with the AI, sail, and amas on my Subaru Outback's roofrack. Now my brothers and Dad are saying how cool it would be to have the TI so we could all go fishing/sailing together.

Would I be crazy to car-top the TI? I could get the trailer hitch and that rear rack extension:

http://www.pickupspecialties.com/Extend_a_truck/extend_a_truck_load_support.htm

I know the TI is heavy, but with 2 people it can't be that bad.
Or would it be wiser to get a 2nd AI down the road? Could I car-top 2 AIs?

I appreciate your thoughts!
Thanks,
Andrew

I don't own a TI, just an Adventure, and not even an "Island". But there is quite a bit of discussion of cartopping the TI to be found online. I like this video, since it's similar to the way I handle my Adventure: