I do not have a kayak, I have a pirogue, but it is basically the same thing. I use it when going hunting in the swamps, and the problem was that I had to be able to haul a 4-wheeler at the same time. You cannot drive up to the water with the truck, and I had to use the 4-wheeler to get the pirogue to the water.
What I did was buy a cheap, light, Chinese made trailer from Northern Tools and convert it to carry the pirogue. I carry the 4-wheeler in the bed of the truck and when I get to the parking area I unhook the trailer from the truck, unload the 4-wheeler, hook the trailer to it & go.
Here is the trailer I bought from Northern:
http://www.northerntool.com/webapp/w...6970_7769_7769
All I did was take off the factory main beam / tongue and replace it with a longer piece of 3" x 3" square tubing. I built a wooden sliding piece to support the nose of the pirogue, and away I went. You can see the cost of the trailer on the Northern website, and the piece of new square tubing from an iron supplier in town cost me about $90. I painted the whole thing camo. It works for me. I also use it to haul long pieces of lumber home from the lumber yard when I need some.
If you would like pics I can take some this evening when I get home.