The reason that a lot of people are not pour molding their own replica inserts is because of the fact that the resins shrink once they cure. You can't take a part, and make a mold based on it, and pour in the resin and expect to get the same exact dimensions on the molded part as the original. For those that know that one stroke of the file will ruin a duck call toneboard, they can see that all of these dimensional changes (smaller) on a pour molded part will not sound near the same as the original part.
Brian