Thought I'd share because y'know, sharing is caring. I spent most of today mucking around with Paint Tool SAI brush settings as well as installing some new ones and managed to come up with a brush that actually replicates fineliner pretty well.
All this brush is, is specific settings. They're are all there next to an example of something I drew with said brush today; the base for the brush is basically a modified version of the original pencil tool (not that I'm too sure what that was considering my pencil tool is modified as well...).
But anyway I hope this will be helpful to other SAI users since settings always seem so fiddly.