Simultaneous spatio-temporal focusing of ultrashort pulses is usually performed by single-channel stretcher-compressor geometries where pulse front tilt leads to spatial asymmetry. Here, the basic approach is extended by superimposing two reciprocal sub-beams in a dual-channel stretcher-compressor setup. Spatio-temporal properties of the symmetrized focal zones of few-cycle near-infrared pulses are studied by parametric numerical simulations with physical optics software. Spatial modulations of focal zones depending on focusing conditions appear. Relationships to specific ultrafast interference phenomena are addressed.