I had the same thought when I did my first boat. I chose a similar (or so the salesman said) roof coating. The first time I launched off the beach, the coating on the bottom was rubbed through. If you go this route, try a scrap patch first and see how it penetrates/holds up. You'll only be out a gallon of paint, not a whole skin.

The next boat I went straight for the hypalon.

good luck!

dave