Variation of total radius, base of convective zone and effective radius under the fifth-force for uncalibrated solar models. Each observable is normalised with respect to its value at 𝒴 = 0 (no fifth force) at a fixed initial helium abundance (Y₀), initial metallicity (Z₀) and mixing-length parameter (α_MLT). Whereas the fifth force has a significant effect on the radius and position of the convective zone, its effect is milder on the effective temperature.