Jag...
JohnB is correct, you can eliminate the bump stear with the servo flat as well as mounted at an angle. The rule of thumb is when you run on a smooth track run the servo flat, if the track is bumpy run it on the angle mounts. Running the servo flat will give more stearing. the angled mounts make it easier to drive. You'll see an acerman change as well as weight position change as well as bump stear change when you try it flat vs. at an angle.
Wayne