gear it to 40mph
find the user BrianG on this forum, he made a gearing calculator for doing exactly this!
make sure it is a good quality lipo too (at least a zippy or better)
should keep you very happy.
but on my revo (same final drive as you have, just different setup)
i am geared 17/56. since you run a lower voltage try 18-20 / 56.
but using the gearing calculator you will be fine.