I haven't yet poured a lure from anything but soft plastic, so I can't help you with your resin question.
By and large, I think you want a surface lure to be as buoyant as possible, to give you the liveliest action, and the most lattitude in ballasting.
But having the lure sit down in the water moves more water, attracting attention in rougher water, or at night, so that's why I seat them the way I do.
I've made them from Douglas Fir, Pine, Poplar, Balsa, and finally PVC decking. For one piece lures, where water intrusion isn't a big issue, wood works fine.
Take a good look at a similar lure that you like, and see if you can't duplicate how it sits in the water, and it's general shape, so you're not starting from square 1.
I've found that weighting them 40/60, so they float almost level with the front 1/3 to 1/2 of the top out of the water is the ticket, at least for me.
Having the center of gravity just past midpoint makes the rear want to keep moving after the front slows down, which is what you need in a walking/gliding bait. I do a preliminary test by balancing the lure blank over a pencil on my workbench. I adjust the weighting of the lure until the balance point is just past the center point. If I had to give a formula, I'd guess 40/60 is about right.
Bigger walking/glide have a lot of water resistence. So the deeper the tail sits in the water, the harder you have to work to get them up and walking, and to keep them walking. Smaller lures, like spooks, can still walk with the tail down, but big ones need some help.
I make my shorter 4" lures hang with the tail slightly lower. That way, they walk the dog better, but they don't glide as far or as easily.
A tip for deciding how to weight a lure is to consider that the longer the lure is, the more water resistence it has, and so the higher you'll want it to float at rest.
My balance point is just back of the mid point, and, taking a cue from the Lunker Punker, and the Pupfish and Dog X before that, I make the shape of the bottom like a flat banana, with the front "chest" flatter, to help get the lure up and walking, and the rear 2/3rds more rounded, to reduce water resistence on the change of direction.
Hope this helps.