Generating an internally 4-connected binary matroid from another

We prove that if N is an internally 4-connected proper minor of a weakly 4-connected binary matroid M with | E ( N ) | ≥ 7 , then either there exists a weakly 4-connected minor M ′ of M such that M ′ has an N -minor and 1 ≤ | E ( M ) | − | E ( M ′ ) | ≤ 2 , or one of M and M ∗ is isomorphic to D n , D n ∖ f 1 , D n , or D n ∖ f 1 .