Calculations of equilibrium radii of Langmuir-monolayer domains are compared with measurements in the liquid expanded/gas coexistence region of myristic acid. This paper extends the works of McConnell [Proc. Natl. Acad. Sci. 86, 3452 (1989)] to higher area fractions Phi of the domain phase. A maximum increase of the equilibrium radius of gas-domains by the factor of 26 on expansion (from dilute towards closely packed domains) is predicted, while the number-density of the domains passes through a maximum at Phi=0.35. The experiments agree with these predictions. Some domains disappear on expansion before domains actually touch each other. A quantitative analysis shows that the line tension between both phases increases by about 10% on expansion.