This used to plague me for a long time. I would think I had even scrapes on both sides of one limb, but when I checked it over later, it would not be even thickness at all. I learned to check it on the tiller and flip the bow around and check the other side, and pretty much do this every single time it went back on the tree. I would just mark the problem areas with one side, then when it is flipped, mark the problem areas on the other side of the limb. Has worked like magic! I used to only check from one side until final tillering but i'm glad I do it this way now. It's like the tiller will tell you what to do to get the thickness taper even.