Before revision:  In a simulation study, we find that our method is most effective when the response model exhibits some amount of "sparsity" with respect to the covariates,but can be effective in other contexts as well, as long as the first-wave sample size used to estimate the stratificationtree is not prohibitively small .
After revision:  In a simulation study, we find that our method , paired with an appropriate cross-validation procedure ,can improve on ad-hoc choices of stratification .