I believe these things are called pool noodles, they are the round colored things you see at the front of Wall-Mart for about five bucks. This time of year you have to go online to get them; I am considering going to solid foam rollers instead of the hollow ones. Putting boats on top of cars inevitability leads to scratches in my experience. I have a Honda Fit, reported to be the cheapest car to drive, with over a hundred thousand miles and hail damage. Hard to tell the canoe scratches from the other scratches. My wife is suggesting a foam sheet to cover the roof. There are some great light weight trailors that wear well and are a joy if extra gear is involved. Don't know if a Jetta can tow.