Sharpen the recurve with a rod, not a flat stone
The inward curve of a recurved edge is out of reach of a flat bench stone, which only touches the high points. Use a round ceramic or diamond rod for the hollow section, holding the same angle you use elsewhere, and sweep a flat stone only along the belly towards the tip. A Damascus steel knife from Pakistan with a 23 cm blade like this one rewards that patience with an even edge from heel to point.
