Good system Eric. I hate making molds. Very boring. I think the dowels are a great work around to fix the problem with the screws pulling out. But one could , since, you are already using machine screws, drill through the mold and nut them on the inside of the mold. Of course they would need to be counter sunk into the mold so they wouldn't interfere with the guitar rims. Very unlikely the screws could pull through the mold.
