Great explanation. Indeed, the "rotation/tumbling" is nothing to worry about. One of our biggest challenges is relaxation. The moment we polarize, the clock ticks. Usually, the time scope is around 15-90s. I'm in the field of para-hydrogen and built automated systems which carry out the chemical reactions, polarization transfers and sample cleaning. Many hyperpolarization experiments with para-hydrogen prefer nasty solvents as chloroform or methanol. It is a technical challenge to replace them by water within seconds. One of my favorite topics is Xenon hyperpolarization. It's very elegant, no cleaning required, no wet chemistry, and provides amazing lung scans.