If the bearing edge/top of snare is not perfectly flat then how much imperfection before it affects the tone? Example, when I place the top part of the snare on a flat surface, there are two areas opposite each other that sit slightly higher. One side sits about 1mm higher, the other 0.5mm but the change is gradual. All my snares are like that to an extent, so I've no point of reference. I actually flattened a cheaper snare but when I re-routed the edge it didn't go too well.