You can carpet the backing plates.
Raising the bunks will increase the space between the boat and the fenders. Going one inch up might give the space you want.
They started with 6 tubes and welded several together end to end to end up with 2 tubes close to 40' long and 2 more in between the main tubes. So it's like a quadtoon.
"B is for build" on Youtube is building a Pontoon Yacht. When done it will be 40' long and 12' wide.
It will have a second level and a hot tub built into the bow. It's an interesting project.