Tdawg answered you well. Changing autosubs will kill everything about how the set plays and I think raising fatigue will just make everything too easy. But, if you're going to mess with one...try fatigue first...maybe you will find something you are happy with (though I am skeptical it will work well).
It's sorta like the warranty on a piece of equipment, you cut that factory seal and open it up....all warranties are null and void.
I like to be flexible on sliders when I can and give people options...this just isn't the year for it....