Printing at a lower layer height or slower speed increases the likelihood that you're trying to print on top of plastic that hasn't cooled. Are you doing anything to ensure a minimum print time per layer, even forcing the hot end off the print if it has to in order to ensure the minimum layer time? Small items can be troublesome to print if you're not managing the temperature of the print properly.

A couple of us have been cutting out the bottom of the fan shroud for the hexagon hot end, eliminating the likelihood of the hot end melting the shroud. A picture of mine is in this post of my build thread - http://3dprintboard.com/showthread.p...ll=1#post26647

After experimenting with various print coolers, I was convinced that the best approach for a cooler is based on a blower, not an axial fan. You want a pretty focused airflow stream coming out of the cooler, and most axial fans simply don't work well with the backpressure created by putting any kind of airflow shroud or duct on them. The blower scheme I'm currently running is documented here - http://3dprintboard.com/showthread.p...ll=1#post26657