Effect of changing mass-loss rate and clumping factor on the Hα recombination line and on the Si IV λλ1393–1402 resonance line, using the best-fit model including optically thick clumping. GA best-fit model – red solid line. Best fit with increased clumping and fixed mass-loss rate – blue dashed line. Best fit with reduced clumping and fixed mass-loss rate – yellow dotted line. Best fit with increased clumping and reduced mass-loss rate – magenta dashed line. Best fit with reduced clumping and increased mass-loss rate – green dotted line.