What is the reason behind the disabled symmetry option in FDTD?

Hi

I want to run an antenna model using FDTD in order to compare results with time domain solver in another s/w. For Feko FDTD solver, the memory requirements are high and the speed is very low. Why is the symmetry option disabled in Feko? Is there an alternative to speed up the simulation?

Thanks & regards

Vishakha Pandharpure