Tell him to rock it "Brah Style": on top of the car, 52 weeks a year, with an assortment of kayak "flair" (stickers) pasted along the windows, bumpers, and of course, rocket box. Once in place, you cannot move it for either function or seasons' changes.
OK- in reality, I recommend slinging the boat against a garage wall on its edges:
Standing it on its end works fine and prevents "oil-canning" as well, but I've knocked over enough boats on-end to dissuade others from making this a regular practice. And don't go out and buy a sling system- get some webbing and some Fastex buckles from REI and make yourself one in 10 minutes.