sorry for the slight thread jack but it's ironic a pic of my old boat was just posted...
I just pulled my boat out of storage today and I tried to take a pic in the same spot - funny to see it here today! Definitely pulling more weight this time around.
Regarding towing with a Cayenne, it's rated at 7700 lbs and you shouldn't have any issues towing any boat under 24' (even without the air suspension). Check out this video of a Cayenne S towing a 911, it's solid ~
http://www.youtube.com/watch?v=IQPNiAB6xbM