Comparisons between the large separations (top) and the small separations (bottom) of the four best-fit models indicated by squares for models with [Fe/H]_s = 0.23 ([Fe/H]_i = 0.30) and triangles for models with [Fe/H]_s = 0.16 ([Fe/H]_i = 0.23). Empty symbols are used to indicate a helium abundance according to Y_g, and filled symbols for a solar helium abundance (see text for details). Observations are represented as white diamonds.