Hey Tallon, I think a good way to build your own sides would be to use a piece of foam board to create the L shape. Then cut a piece of PVC pipe to simulate the indentation. Covering the inside with green masking tape. Creating a tape and foam board mold. When you lay the fiberglass in there it will be the finish piece. The tape will help you release your piece and the fiberglass resin will be easy to sand smooth. That's just my humble suggestion. Thanks for looking I appreciate your input...dave