Have you got a set of vernier calipers? The cheap digital ones on eBay work fine and I'm always using them check stuff on my builds. They're just the easiest way I find to check thicknesses and diameters etc. I'd check the neck depth at both sides at that end, and also the two sides of the neck pocket. Whichever is the most uneven is the one I'd tackle. Both surfaces want to be as flat as possible, regardless of any angle.