Redtails thanks for that, not something that would have crossed my mind so on a learning curve here. See I always thought that "engineered" stuff was always accurate and only changed with temerature ( a bit like the steel rule that is accurate at 11 degrees) so thank you for pointing this out and opening my eyes.
I have to say that I always use a drive centre in the morse taper, I normally use a steb centre, especially if I am teaching as they are more forgiving in the event of a catch. I still use 2 and 4 pronged centres but normally those are used on big pieces of spindle turning. I also do such a variety of turning during the week that some times a chuck is only on the lathe long enough for me to make one cut! If I am going on holiday I always remove morse taper drives and chucks from the lathe.