Demonstration of the χ² convergence for the fundamental band for each of the six primary parameters for Model PP at day 385. For each panel we keep the optimized parameters the same except for the parameter being varied. For panels (A)–(F) we only show χ² of the fundamental band because the overtone is virtually nonexistent. (A) Density structure (n), (B) inner velocity edge (v₁), (C) width of the molecular region (Δv), (D) clump density contrast (f_c), (E) clump size (r_R), and (F) clump shape (ϵ). For discussion, see Section 4.2.