Using the same approach as for R3, we considered the DA reaction between cyclopentadiene and acetylene (R4, Table ), for which comparison to experimental gas-phase kinetic data is possible. Performing MLP-US enabled us to obtain quantitative accuracy in both enthalphic and entropic contributions. These results show that MLPs, in combination with US, enable us to achieve accurate free energies with associated errors, and treat anharmonic effects without ad-hoc corrections. While the MLP fitting and US protocol was completely automated and achieved within a day for this reaction, the choice of the QM reference method remains a critical choice that still requires human intervention.