Those keychains would probably rip out first try. For less money you could buy actual scupper plugs https://www.amazon.com/Amarine-made-Pack-Universal-Kayak-Scupper/dp/B0787K67MN/

How many do you need for your Tamarack? I used to have a Tamarack and only kept the two scuppers under the seat plugged up. I sold that kayak (with the 2 scupper plugs in it), but have 2 scupper plugs left over that I don't use. I can mail them to you if you want, I have no use for them anymore.