The "plugs" I found just push in very much like the plastic plugs that come with furniture you buy and have to assemble to plug the hole where you installed a screw. My Lowes also have plastic screws that could be screwed into the threaded holes. I usually put the extra knobs in a plastic zip-lock bag and store in the storage compartment of the NuCanoe. That is what I use to do when I owned the older NuCanoe and now that I own the Frontier 12, I no longer have to worry about the threaded holes since the Frontier 12 has the track system for seat placement.
Fly fishing and fly tying are two things that I do, and when I am doing them, they are the only 2 things I think about. They clear my mind.