hifi28 - Your room proportions aren't bad, and if you can get some insulation above your drop ceiling, it could be fairly good. Biggest limitation is the 11.5' dimension.
CS2s are wide-dispersion transducers, so your best bet is to put the speakers on the long wall. You also need them about 3' from the wall behind them, which puts your listening seat against the other long wall. That can be OK IF you can get a sonic hole behind your head, such as replacing drywall with acoustic tile to allow the back-wave to continue through the wall rather than reflect from it.
Can your room accommodate that?
The other option is short wall speaker placement which would require significant absorption / diffusion at the side-wall first reflection points. That could work.