Thanks for your response. The purpose of the power calculations is to determine the sample size required to replicate the current significant result (a similar approach as described here: Power calculation for replication sample). I am using the function wp.regression() from the WebPower package to make the power calculation for each regression, and this function uses the statistic f2 which requires R^2 from the model both with and without the variable of interest. For this R^2 calculation, would you suggest I use the function brms::loo_R2() instead of brms::bayes_R2()?