I've never detuned the middle of the board. If you're a rail rat I can see wanting to detune that part of the edge. A pipe, or freerider I would say ooops! You can get an edge sharpener and sharpen it up in that section. If you get a good edge sharpener, don't grind your edge off. Otherwise you're going to need a base grind.
The other solution is just ride powder all the time. You don't need edges for that...