  We show any matrix of rank $r$ over $\mathbb{F}_q$ can have $\leq
\binom{r}{k}(q-1)^k$ distinct columns of weight $k$ if $ k \leq O_q(\sqrt{\log
r})$ (up to divisibility issues), and $\leq \binom{r}{k}(q-1)^{r-k}$ distinct
columns of co-weight $k$ if $k \leq O_q(r^{2/3})$. This shows the natural
examples consisting of only $r$ rows are optimal for both, and the proofs will
recover some form of uniqueness of these examples in all cases.
