So I have a perfect part printed at 0.6 layer heights and 0.6 layer width. No STL modification necessary.
The fact is, the flow rate requirement seems to be dramatically different depending on the layer width. I guess this is a firmware issue (Repetier for me) rather than a Slic3r issue.
With 0.6mm LH x 1mm LW, a flow rate of 82% gives perfect results.At 0.6mm LH x 0.6mm LW, the ideal flow rate for me is 110% !!
It is because of this that my attempt to resolve the xy detail issue by printing narrower perimeters could never work.
There is not a flow rate (extruder steps/mm) that works for 0.6mm LW perimeters and 1mm LW for everything else. The only solution is to do a default LW of 0.6mm and up the flow rate.
The upshot of all this is that some prints (top and bottom corners, tool mount so far) need a narrower LW and corresponding increased flow rate. The difference in print time is :
0.6mm LW, 0.6mm LH, 110% FR: 34m
1mm LW, 0.6mm LH, 82% FR: 28m
This part is listed as taking 2:06 on the parts page. Strength tests maybe to follow, but the parts seem f*cking strong.
Edit : the given flow rates are in relation to a 100% flow rate (steps per mm) arrived at via calibration and tweaking on my E3D v6 all metal universal hotend.