prpp3[1] - prop_prong_h + prp_r5 ];
prpp6 = prpp4 + [0,-1] * (prop_prong_h +
prop_prong_heel_slope * (prpp5[0] - prpp4[0]));
prpp8 = prpp4 + [0,-1] * prp_r8;
prpp9 = prpp8 + [-1,0] * prp_r8;
prpp3[1] - prop_prong_h + prp_r5 ];
prpp6 = prpp4 + [0,-1] * (prop_prong_h +
prop_prong_heel_slope * (prpp5[0] - prpp4[0]));
prpp8 = prpp4 + [0,-1] * prp_r8;
prpp9 = prpp8 + [-1,0] * prp_r8;