+P4 = Q0 + [ -(openingedge_dia/2 + opening_protr_slop + ourcirc_r), 0 ];
+P3 = [ P4[0], Q0[1] - openingedge_dia/2 + opening_protrh
+ - intooth_top_slop - ourcirc_r ];
+P2 = P4 + [ -(inside_len - ourcirc_r*2), 0 ];
+P1 = [ P2[0], P3[1] - (inside_h + ourcirc_r*2) ];
+P9 = [ outside_len - ourcirc_r, outside_gap/2 + ourcirc_r ];
+P8 = P9 + [ 0, outend_height - ourcirc_r*2 ];