Dang! Marling got me into making lures too! LOL I make them from wood. However, I have designed a few in Fusion 360, just for the fun of it. Never got around to printing or using them though. I believe your initial design would have worked if you would have added more weight in the belly. A lure tends to lay over if it isn't ballasted properly. Have you thought about using twist-eye hinges like Marling uses? Then you could paint and completely seal each half before joining them together. Fun video to watch!