  A $\beta$-beam with maximum $\gamma=150$ (for $\helio$ ions) or $\gamma=250$
(for $\neon$) could be achieved at the CERN-SPS. We study the sensitivity to
$\theta_{13}$ and $\delta$ of such a beam as function of $\gamma$, optimizing
with the baseline constrained to CERN-Frejus (130 km), and also with
simultaneous variation of the baseline. These results are compared to the {\it
standard} scenario previously considered, with lower $\gamma=60/100$, and also
with a higher $\gamma\sim 350$ option that requires a more powerful
accelerator. Although higher $\gamma$ is better, loss of sensitivity to $\theta
_{13}$ and $\delta$ is most pronounced for $\gamma$ below 100.
