Out-leaf extension conjecture for maderian digraphs

Let $F$ be a $\delta^+$-maderian digraph and let $v_0\in V(F)$. Form $F^\ast$ by adding a new vertex $v_1$ and the arc $(v_0,v_1)$.

Out-leaf extension conjecture. The digraph $F^\ast$ is $\delta^+$-maderian as well.

This is described as an important step toward the forest-orientation conjecture and remains open in the supplied text.