Finite-Size Scaling of Frustration-Density-Wave Ordering: Coherent Crystallization Does Not Survive, but Persistent Finite-Q Instability Does

We perform finite-size scaling of gauge-invariant constrained minimization of the Wilson plaquette action on diamond lattice supercells with SU(2) holonomies, extending from 4x4x4 to 6x6x6 and 8x8x8. The coherent single-mode frustration-density-wave (FDW) crystal reported at N=4 does not survive scaling: energy reduction shrinks from 29-54% to 5-13%, and the dominant Fourier mode power collapses from 90% to below 2%. An independent optimizer comparison using multi-start L-BFGS-B, basin-hopping, and staged annealing confirms that this scaling trend is predominantly physical, not an artifact of optimizer failure. However, persistent spatial modulation (std(F) = 0.3-0.5) and finite energy reduction (5-13%) survive at N=8, indicating that the finite-momentum vacuum instability is a genuine but incoherent effect, qualitatively reminiscent of frustrated or glassy systems rather than crystalline order.