I bought a TI 2010 and was on the water (Sweden, around Stockholm and lake Mälaren) for two months, without ever sleeping on the ground! I slept on a sleeping mat in the rear seat. I am 170 cm long. I put my feets on the bar in front of the rear seat or bent my legs to get them inside the place. Not extremely comfortable, but I slept well! I had a tarpaulin which I quickly rolled out over myself and the luggage in the front seat when it started to rain.
I did not even leave the boat for making food. Never cocked anything! I just ate stuff which was easy to prepare and eat in the boat. So I seldom left the boat. Had a great time. Could have stayed out very much longer, but autumn arrived.
It seems quite possible to rise a tent on the trampolines. I'll try it next summer. I might even travel to the U.S. and buy another TI and sail along the coast.