Borel-Tukey morphisms between Ramsey homogeneity relations

We study Borel-Tukey morphisms between almost-homogeneity relations. For finite $r,s\ge1$ and $m,n\ge2$, we give the complete one-stage classification: $\mathbf{Hom}^r_m\to_{\mathrm{BT}}\mathbf{Hom}^s_n$ holds exactly when $r>s$, or when $r=s$ and $m\ge n$. Our main result is that binary triple homo