Suction cups suck... in a bad way.
I purchased a two-pack of these suction cup fender straps. I'm now down to one as the other is probably well on its way to the Atlantic Ocean about now (along with the fender). Thought it was a great idea, but it just didn't work out. I applied the suction cups to a clean, smooth (gel coat) surface, expecting it to hold... and it did, for about 15 minutes, then was gone. I removed the survivor and secured the fender the traditional way, with a line and cleat. To be fair, the water was pretty choppy due to a bunch of jet-skis creating unwelcome wakes. The boat was beating against the dock pretty good. But, a traditionally secured fender would have survived the punishment.