I'd agree with what everyone else has said. Putting the speakers with the windows behind them would be the best layout. That should give you a fairly symmetrical radiation pattern between left and right speakers. Symmetry is very important to stable soundstaging.
And yes, some thick curtains would be important. As would some absorber panels or diffusers in the first reflection points.
And yes, some thick curtains would be important. As would some absorber panels or diffusers in the first reflection points.