In the context of hydrogenative PHIP there are several possible ways of exploiting ULF to transfer polarization. The most commonly used method utilizes adiabatic sweeping of the magnetic field either from near-zero values to a few µT, or from negative to positive ultra-low fields. This approach, often referred to as magnetic field cycling, or MFC, has proved to be one of the most efficient and robust techniques of PHIP transfer . Its performance is further enhanced when the linear field variation is substituted by so-called "optimal" profiles. The latter take into account the field values where spin mixing occurs most efficiently, and where the rate of the field sweep should be reduced to preserve the adiabaticity of the polarization transfer. Rodin et al. have addressed this challenge by introducing the concept of "constant adiabaticity" profiles. The authors optimized the field sweep profiles for PHIP transfer in C-fumarate and achieved better efficiency compared to linear sweeps. However, the calculation of such "constant adiabaticity" profiles requires a precise knowledge of the parameters of the spin system, which is often not so straightforward. Moreover, such calculations become impractical for larger spin systems that we often encounter in PHIP experiments with non-isotopically labeled substrates.