Nice write up. The bed extender I use is a lot less expensive. If you don't need it to go above the tailgate you might consider it.
http://www.harborfreight.com/cpi/cta...emnumber=39168
Also, you might mention the need for marking the end of the kayak since it sticks out past the legal length of the vehicle. For daytime, it needs a flag, for night it needs a light. Since I hit LJ pre-dawn I'm always driving down in the dark. I made up a bar with full trailer lights which I bungee right at the tail end of the kayak. That way if some driver is coming home from his party bleary eyed at 4 AM and crashes into the back of the 'yak, I'm covered.