I was playing with the single extrusion settings and came across an interesting flaw/compromise.
The circular features of this design give different results based on single extrusion settings. Each one compromises quality in different areas. When "External Thin Wall Type" is set to "Perimeters only," the sides of the circle get cut off and single extrusions do not occur for edges on the top layer. When set to "Allow single extrusion walls," the top layers look good but the circular feature is left with floating edges. This remains true no matter the "Minimum Extrusion Length."
Hopefully these pictures help explain.
(Green is the desirable outcome and red is not desirable)