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Nested wire-array loads on Z with a high degree of azimuthal symmetry in the outside current-return-shell (which surrounds a z pinch) exhibit a 6±2 azimuthal mode structure in the axial X-ray emission near stagnation when the pinch is viewed from above through a small radiation-exit-hole in the anode. MACH3 numerical simulations show that if a low-number mode like 6 does exist in the initial density distribution, it will remain throughout the implosion, amplifying near the time of stagnation. And if a random-density pattern initially exists with a significantly higher mode number, it will coalesce to a reduced mode number of about 4 to 8 by the time stagnation is neared, in agreement with experiment. Current-return-shells with a nine-fold periodic slot structure (which permit side-on viewing of the pinch) are used as examples of loads that develop azimuthal mode structures in their X-ray emission.