Such as best seen in FIG 2 the transition between convex surface 16 and {TAIL ~ the area} confined by the surfaces 1 a, {HEAD ~ 1 b}, 1 c is formed by an upwardly inclined planar surface 17, which should be inclined 30° 55° relatively to the neutral plane P 
Such as best seen in FIG 2 the transition between convex surface 16 and { TAIL ~ the area } confined by the surfaces 1 a , { HEAD ~ 1 b } , 1 c is formed by an upwardly inclined planar surface 17 , which should be inclined 30 ° 55 ° relatively to the neutral plane P
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