Optimization and testing the described methods of PHIP polarization transfer is a non-trivial task. A major complication is the gradual loss of the signal enhancement throughout an extensive set of experiments due to the depletion of substrate molecules and the degradation of the hydrogenation catalyst. This complication does not arise for single-shot experiments when a small amount of substrate undergoes complete hydrogenation in a single pH2 bubbling experiment. However, the single-shot approach is impractical when one needs to repeat the experiment several times or when some experimental conditions must be optimized. For this reason, we started by testing the described protocols in repeated experiments where the substrate was in excess relative to the catalyst. Using 200 mM substrate and 1 mM catalyst allowed for 30-40 repetitions with sufficient levels of hyperpolarization. Throughout the optimization of the experimental protocols, we recorded 3 to 5 reference points with the same values of all parameters to monitor the inevitable decay of the PHIP enhancement due to catalyst degradation. After all optimizations, a set of single-shot experiments was performed to determine the highest possible C enhancement that can be achieved with any chosen PHIP transfer method. For this we used 10 mM of substrate and 4 mM of catalyst, ensuring that all substrate undergoes complete hydrogenation. All the presented dependences of C polarization on experimental parameters are normalized to the highest level of C polarization in the corresponding single shot experiment. Each experimental solution contained [Rh(dppb)(COD)]BF4 (Sigma-Aldrich, 341134) dissolved in 600 l acetone-d6 as catalyst precursor.