Experimental: multigrid runs balance their finest-level cells across ranks. The finer levels inherit ownership by refining the coarsest level's split, and PETSc's default compounded its remainder, e.g. 33/36/32/27 cells per axis for 128 cells on 4 ranks at three levels (1.42 times the mean on the busiest rank of a 4 x 4 x 4 layout); grid setup now chooses which coarsest ranks take the extra point, giving 33/32/32/31, with the same feasibility limits.