- z1 = (0, 2 staff_space) + center;
- z2 = (0, - 1/2 staff_space)+ center;
+ bottom_overshoot = stafflinethickness;
+ bottom_stem_thick = 1.2 stafflinethickness;
+
+ z1 = (0, 2 staff_space) + center - (0, stafflinethickness/2
+ + clearing);
+ z2 = (0, - 1/2 staff_space - stafflinethickness/2 )+ center;