The custom mainshaft combos are a great way to go when looking for that holeshot from a dead stop and having closer ratios. The lower second gear (2.35, 2.25) has the feel of a close ratio, but from my experience most speedster owners are not looking for a drag race combo out of the hole. The berg five allows the driver an extra gear to down shift from fifth to past a car or be in the torque curve of the motor why cruising the twistys. I have ran several five speed combos. With a 4.12 r/p and 3.88. The 4.12 combo worked good with a .082 fifth. It was a stop light to stoplight runner with a 1.70 third and 1.30 or 1.21 fourth. That same r/p worked well with a 1.54 third. This is with a 3.78/2.06 mainshaft.
the 3.88 combo worked fine with .089 fifth, 1.14 fourth, 1.48 third. I had it with a 1.54 third but it worked better with the 1.48.