Sigma 150-600 sport fine tune auto focus with dock

[timbo2410]

I've been trying to fine tune the auto focus and I've had great success with tuning at the shorter 2.6 and 6 meters. The 15 to infinity however are causing problems. Using the same methods as the 2.6 and 6 meters ranges (with spyderlenscal), I can have what appears to be a good adjustment on focus. The infinity is quite hard as at that distance it's all rather blurry (50 meters) .. if I then try and take photos at either 15 meters or infinity, the focus is off. If I then try and adjust for this, then I never seem to be able to get a final figure .. at my best efforts I then tried the 1.4x tele .. hahahaha omg .. the focus error is of course just compounded .. anybody else having success ?? and no the lens is out of warranty ..