OK I seem to have made a breakthrough. Lens seems to finally be functioning correctly at all focus distances wide open.
I downloaded and installed magic lantern onto my CF card and installed it on my camera. I then downloaded and installed the latest magic lantern nightly build (as dottune is not in the normal version of magic lantern yet). I then ran dottune via magic lantern for the 4 distances required for the dock. The process is fully automated and seems very accurate.
I ended up with +1, +6, +8, -2
I put these numbers into the dock software, updated the lens and set my body MA back to 0. I then set up the camera at a random distance from the target and ran the automated dottune again as a check and it came out as 0. RESULT!
I have been taking test shots for about an hour of real subjects hand held and it seems to be spot on. I'm now a happy camper!
If sigma release an ART version of the 85 1.4 that can be dock calibrated I will now be buying it. I had the existing version but sold it due to AF issues
THIS is great news!!