I'm no kayak expert but it seems to me that a kayak would survive a lot better in your system than the average box. They're pretty sturdy. Not sure about what that thing is on top though.
One of the Hub guys working Saturday Air informed me that you cannot be forced to handle live animals. I had a box of crickets going to Petco. I had never heard that before. Is it the same for fish?
I deliver Koi for fish ponds on a regular basis and I see cases of tropical fish going to pet stores. I have delivered frogs, turtles, honey bees, meal worms, and boxes marked "reptiles" too.
I know of a guy that once bought a removable hard top for a convertible car on ebay and all he did was have the person selling it tape a UPS label to the top of it.
The hard top was involved in a roll over accident, so it was already damaged. UPS couldn't do any worse to it. It was accepted, and went through the system.
we had a couple cases of "large live leaches" (as described on the box) come through and the box was damaged so it had to be repacked, those were monsters. gross.
Someone's picking up kayaks. Opened my TP60 yesterday and had two of the dam things to deliver. Took a separate trip and 28 extra miles but I got the job done. Thanks Amazon.