Two methods for studying the rotation/torsion coupling in H-5(+) are described. The first involves a fixed-node treatment in which the nodal surfaces are obtained from a reduced dimensional calculation in which only the rotations of the outer H-2 groups are considered. In the second, the torsion and rotation dependence of the wave function is described in state space, and the other internal coordinates are described in configuration space. Such treatments are necessary for molecules, like H-5(+), where there is a very low-energy barrier to internal rotation. The results of the two approaches are found to be in good agreement with previously reported energies for J = 0. The diffusion Monte Carlo treatment allows us to extend the calculations to low J; and results are reported for the three lowest energy torsion excited states with J <= 3. For the level of rotational and vibrational excitation investigated, only modest changes in the vibrational wave functions are found. The effects of deuteration are also investigated, focusing on D-5(+) and the symmetric variants of H4D+ and HD4+.