I just want to add why they usually have more down than up....

When flying inverted you are already using part of the down elevator travel by pushing. Usually the difference in the amount of down required to fly level and the full rate should equal the "up" rate or be somewhere close. It's so you can have down travel equal to up travel with the required amount down to maintain inverted flight compensated for.

I hope that makes sense! If not maybe someone else can explain better Granted, a good 3D plane will require very very little down elevator to fly level inverted due to CG placement.