I always felt that the autoscroll is too sensitive when in fullscreen mode. Going through the source, I found that it was hardcoded to 10, so I attempted to make it a preference. Personally, I am finding it much easier to work with fullscreen mode, when the thickness is set to 1 and scrollbars are hidden.
The attached patch is just a POC, as I have zero experience programming on Mac OS X. All the code that I added was simply copy paste of existing code.
Please let me know if you need the source in an alternative format.