Parameter correlations for the lamppost model (Model 4 in Table 3). Shown are the χ² significance contours for the two parameters of interest. First row: jet base height h in units of GM/c² versus the black hole spin a. Second row: inner disk inclination i expressed in degrees versus the spin a. The values clearly point towards a high spin value. Third row: inner disk inclination i versus the jet base height h. Shown are the χ² significance contours for two parameters of interest based on Δχ² = 2.30, 4.61, and 9.21, i.e., 68%, 90%, and 99% confidence, with respect to the best fit case.