I've found that for light weight things that need attachment to the boat fiberglass is to just use that 3M double sided sticky padded tape stuff. It holds like mad and you can remove whatever you've got stuck on the wall without having a hole to contend with. I'm going to be installing my own paper towel holder myself shortly, and that's the way I'm going. I'm tired of patching holes.
"There's a wind in my sails that protects and prevails." - "Six Months in a Leaky Boat", Split Enz