Previous work (Robinson 2022 Plasma Phys. Control. Fusion64 105014) has shown that there is a regime of ion beam transport in plasmas where the electron–ion drag becomes so intense that the electron temperature rapidly rises to temperatures at which the electron–ion drag is strongly reduced. This regime is mainly thought to pertain to short-pulse laser-generated ion beams, because of the ion energy fluences required to enter this regime. The regime for was thought to be determined by a dimensionless number, . Here it is shown that there is another dimensionless number that needs to be considered. Numerical simulations show that this dimensionless number, χh, does not affect the half-energy range of the ion beam, but does determine how strong stopping is at the ion beam front, and thus how rapidly the beam energy falls past the half-energy range.