  Terzan 5 is the only Galactic globular cluster that has plausibly been
detected in the very-high-energy range. Stacking upper limits by H.E.S.S. on
the integral $\gamma$-ray flux of a population of other globular clusters are
very constraining for leptonic cluster emission models. We demonstrate that
uncertainty in model parameters leads to a large spread in the predicted flux,
and there are indeed regions in parameter space for which the stringent
stacking upper limits are satisfied. We conduct two more case studies: we study
the uncertainties in differential TeV flux for M15, showing that our model can
satisfy the stringent MAGIC upper limits for this cluster, for typical cluster
parameters. We also calculate the differential flux at TeV energies for
$\omega$ Cen, from which five pulsars have recently been detected at radio
energies. It is thus important to increase measurement accuracy on key model
parameters in order to improve predictions of cluster fluxes so as to better
guide the observational strategy of the Cherenkov Telescope Array.
