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The heterocyclic bisdithiazolyl radical 1b (R₁ = Me, R₂ = F) crystallizes in two phases. The α-phase, space group P2₁/n, contains two radicals in the asymmetric unit, both of which adopt slipped π-stack structures. The β-phase, space group P2₁/c, consists of cross-braced π-stacked arrays of dimers in which the radicals are linked laterally by hypervalent 4-center 6-electron S···S–S···S σ-bonds. Variable-temperature magnetic susceptibility measurements on α-1b indicate Curie–Weiss behavior (with Θ = −14.9 K), while the dimer phase β-1b is diamagnetic, showing no indication of thermal dissociation below 400 K. High-pressure crystallographic measurements indicate that the cross-braced π-stacked arrays of dimers undergo a wine-rack compression, but the dimer remains intact up to 8 GPa (at ambient temperature). The resistance of β-1b to dissociate under pressure, also observed in its conductivity versus …