For anyone interested I have always car topped my AI, my partner and I live in a motor home (ex council bus) and we tow a large car trailer with the AI on top and my tools, camp gear in front and Subaru Forester on deck. We are planning to leave the bus and do some slightly remote camping and sailing. The problem I was faced with was the lack of room for camping gear when the car is loaded with the TI. We had looked at the folding trailers and I just do not have the space for it on the trailer, I have ordered a kayak trailer from boat hoist.com. These weigh only 38kg and come apart to pack into two easily managed parcels. They come with cross bars spaced at 1700 mm for the Hobie cradles to bolt to, they will take boats up to 6 meters long.
Down side is they don't come with lights. For anyone else who is space or weight poor these are a must look.
All this said I have not yet taken delivery!