I would re-do what you have accomplished but bond the panels to be molded with Hot Glue/Epoxy instead of Bolts/Rivets (less finish work)smooth the seams and make a "Rough Positive"(make extra heavy and reinforced)of the original then fix the undesirable features of the "Rough positive". Once satisfied with the quality of that make a part. In this part you will find anything you missed in the "Rough Positive". At this point you can just fix the part and use it or fix the part to exactly what you want and make another "finished positive". Then when you make a part it should not require any repairs...always thought about doing this on mine but didn't ever get to it.