"Did some sanding to the front and back today. The wood is starting to look really nice! I went to 220, but will likely go a little finer - 320 or 400 - before I stain. I also smoothed out some of the edges on the back for a belly cut. Used 60 grit and 80 grit to shape, then 220 grit to smooth."

Careful going much higher than 320, it can cause issues with stain penetration as the wood surface gets too "polished" and the stain won't take. 240-320 should be fine for it, again depending on stain type.
Have you checked for glue spots etc? These can be problematic as they will repel stain and stick out like a dog's whatsits. If you find these you can usually get them out with a product called Goof Off and a small clean manual wire brush.