I did this with a single island for a cross country trip without having to haul a trailer and it worked pretty well with only me loading. I think some version of it would work with a tandem but I haven't tried it yet.
First, I already had an extend-a-truck. Not this one but similar:
viewtopic.php?f=73&t=40698I used a hole saw and drilled a 1 - 1/8" hole all the way through the cross bar, top to bottom, about 3" from the end of both ends of the cross bar.
In one of those holes I insert an upright 3/4" pipe about 18" made by screwing a 6" inch nipple and a 12" nipple together with a threaded coupling. When you drop the pipe in the top hole, the coupling will keep it from falling through and you will have a 12" pipe sticking up. That will keep the boat from sliding off that end of the bar while you load it.
For the other end of the crossbar, I bent a piece of 3/4 inch ridged pipe about 6' long 90 degrees and threaded a 6" nipple on one end of it, so when I insert it in the cross bar, the same thing happens. It doesn't go all the way through, it has an upright that will keep the boat from sliding off that side of the bar. With an eyebolt in the top end of this bent pipe, it gives me a place to hang a hoist that's about three feet above the center of the crossbar. I used a simple block and tackle made from an old mainsheet and a couple of blocks to reduce the effort required to lift the boat.
To load the boat, I take off the amas and akas. I put a wheeled cart under the stern, connect the hoist to the bow, lift the bow with the hoist until the bow clears the bar and then shove the boat onto the car, letting out on the hoist as it moves forward. Then remove the hoist and pipes and throw them in the back of the car. Strap the boat and everything else onto the crossbars. I can do that single handed with an AI.
Were I going to do this with a TI on a regular basis. I think I would see about getting a receiver put on the front of the vehicle, put an extend a truck on the front and back, and maybe put the hoist on the front with something on the back to guide it all the way up.
Honestly though, if you want to enjoy this boat and use it regularly, buy a trailer. I have three at the moment, all PWC trailers bought off Craiglist in the $500 range and modified for kayaks, including one for a TI.