[Snake]

It should depend on the weapon type you're holding in your main hand, imo. The weapon's range and/or if it's melee or not is a good way to define how many tiles you want to be away from your target on a back attack.

Or even, maybe make it so that the back attack makes your first movement not consume any Momentum (a free, one-time Electrocharge effect) if you're using a gun or a bow?