I dont have a pontoon, but wouldn't get a small one, I got 3 , one is 56 inches, two are 30 inches, the 2 small ones together are not enough for my 18 foot boat, in 15 to 20 mph winds, I have to use all three, If I get another one, it will be bigger than 60 inches, When I go fishing I dont want to stop fishing just because the wind got up. I would get 2 of the bigger ones for the pontoon, 72 or bigger. I'm on the water long after most people have left because of the wind.

I would mount cleats on the top rail on both sides to hook the rope on, they dont need to be over 5 foot or so behind the boat, put big float on the rope of each one, so if one came loose , the rope would float and you can get it back, I lost one a wateree because I didn't have floats on the rope. They will sink!!!!!!!! Eagle Claw sells 2 in a pack at academy for about 4 dollars, I put 2 on each rope.