  We study a Hyperinflation model involving a field doublet on a hyperbolic
field-space manifold and an exponential potential, providing a concise
treatment of the evolution of the entropic and adiabatic perturbations around
the homogeneous hyperbolic attractor solution. We find that the adiabatic
spectral index narrows down the admissible values of the potential's slope to a
very small region, severely restricting the state space of the allowed
background solutions.
