Problem: I want to be able to fine tune the positioning of my plot legends.
Solution: Use the legends as a Locator in Mathematica.
Second problem: I want to position the legend outside the graphic. It is easier to use scaled points for locator positioning and these work within the plot.
Solution: Surround your actual plot with an empty graphic that acts as a canvas
Below is an example using a toy legend.
The Mathematica notebook can be downloaded here.