[SpEEdyBL]

No, no, no, don't go 5s. There are a few good reasons why 4s is better in your situation. For one, the amount of power available is way, way to much for any type of track. You don't want something that is comfortable for 50-60 mph when you are spending most of the time going less than 30 mph. With the low throttle that you will be using most of the time, you will be heating up the esc a lot. Even if you geared way down, the motor will be spinning for nothing, and eat up your packs in a hurry. Reason 3 is the fact that 5s is taller than 4s. You want the lowest center of gravity for the best handling.