when you design a part to be 3d printed you have to choose the wall thinkness to divide equally into the extrusion width you plan to use.. if you have a .2 nozzle the the smallest wall thickness you can expect to accurately print wound be .2 Making a nozzle extrude a thread thinner than the opening of the nozzle does not work well. Also tapering does not work well whey you are using FFD fabrication due to the layer on layer function of the process.. You should design the part the proper size, it makes life much simpler.. Also the orientation of the part on the build platform and knowing how the slicer works will help you work around SOME of the FFD short comings, but that takes time and patients.
Good luck!