AdrianM:
This is what I got from Josh from the same Q...
On low traction - the servo flat is best.
On higher bite tracks and/or bumpy tracks it's best up on mounts.
From looking at lots of pics from Cleveland, it's a big mix of both.
I tend to like it flat, but I do run mostly carpet.
It affects bumpsteer alot.
And for me, adjusting TOE is a great tunning add for 12th.