The 'belly' of the blade almost always sharpens up quicker; at least it does for me anyway. The key is to watch the edge in all sections, and shift your focus to areas that need more work, instead of making repeated sweeping strokes along the full length of the edge. The belly on most blades will almost always be thinner steel, so it'll grind down more quickly. This is compounded by the small contact area with the stone in the belly, which amplifies the perceived change in edge profile as you continue to grind. It can definitely flatten out, if not paying attention as you work. The very tip and the heel of the blade are the areas that usually take the longest to apex, and therefore need more attention. If using full sweeping strokes along the full length, pressure used in the belly area should at least be very, very light as you 'skim' over it. The flatter mid-section aft of the 'belly' can usually tolerate some more grinding, but also sharpens up pretty fast, leaving the heel and very tip of the blade as the areas needing additional work.
David
