by having: Sc1 always proximad of the middle of cell r (vs. Sc1 at the middle cell r); R2+3, almost at the same level of M1+2 forking, oblique R1 (vs. R2+3, clearly proximad of M1+2 forking, perpendicular to R1); bM1+2equal to dM1+2 in length (vs. bM1+2 shorter than dM1+2 in length).