Lots of good info and advice given here. It would take me a week to put my thoughts down on the subject in such a way that would be helpful. I have a tendency to talk in circles and am much better at building than explaining things. I don't have a physics degree or any knowledge other than what I've learned through many years of screwing up.
My advice for any new builder is to try to duplicate an existing bait that is a known producer. Templates for different styles are out there if you look around online. My first builds were a Shad Rap profile that I was able to find this pattern for. By duplicating the dimensions both in body profile and lip, the angle of the lip, line tie placement, and the ballast weight placement, it took a lot of the guess work out of trying to start off with my own unproven design. If nothing else, it's a confidence builder when you see promise in your very first build. (This bait is a mid diver but just using it as an example)
Keep in mind that the materials used are a big factor also. In other words, if you are replicating a plastic bait, you can't necessarily expect it to behave like a copied wood version. The same goes for different types of wood that all have their own weight, buoyancy, etc. I began with balsa wood, as the original Rapala's are also Balsa. Since then, I've been able to learn the characteristics of some different wood types and bait designs. Most all of what I use now is red cedar.
One things for certain, there is no such thing as being "learned out" when it comes to building baits. It's a never ending process of trial and error and why I enjoy it so much.