The MF-conjecture for F-divisors on the moduli space of stable pointed rational curves

Let ${\overline{\mathnormal{M}}}_{0,N}$ be the moduli space of stable $N$-pointed genus-zero curves. An $F$-divisor is a divisor that nonnegatively intersects every $F$-curve; let $K_{{\overline{\mathnormal{M}}}_{0,N}}$ denote the canonical divisor, and let an effective sum of boundary classes be a nonnegative linear combination of boundary divisor classes. The MF-conjecture. Every $F$-divisor on ${\overline{\mathnormal{M}}}_{0,N}$ has the form

$$cK_{{\overline{\mathnormal{M}}}_{0,N}}+E,$$

where $c\geq 0$ and $E$ is an effective sum of boundary classes. This is introduced as a reduction of the F-conjecture for moduli spaces of curves; the supplied source does not indicate whether the assertion is resolved.