Brush 9 is a superfast fineliner. Best for inking imho.
More opacity responsibility and it's a very nice pencil too.
No visible spacing.
When drawing very fast I got this on release pen:
Lines are drawn from top right to left bottom.

- Line-Up.jpg (190.18 KiB) Viewed 13010 times
It's a bit better with the airbrush (due to default settings I guess)
Anything I can do against that in wacom settings?