There is a cleat inside. The roller I designed is in a U for structural strength. And The whole boat is made of plastic anyway. I could make the bow roller out of 3/8" SS, but it still has to bolt to plastic somewhere.
You may want to consider using a fastener as shown. I couldn’t think of the name of them but I have seen that in one of my canvas books. They are made up of ¼ ‘’to 3/8’’ dowel and small cordage or bungee.I don't like the steel twist locks that the old one has to secure it. They seem to be designed to cut through the fabric in high winds. What is the best way to hook the cover together under the boom?