I was responding to the suggestion that screw pitch and diameter had to be used to calculate the layer heights that you could print at. The reason folks were exploring these calculations was to reduce z-ribbing which, in the end, was determined not to be effected by this and was discounted. A layer height of 0.2mm is the 80% target range for a 0.25mm nozzle and would be, imho, a good place to start with this nozzle. Sorry if I wasn't a bit more clear.