The concept of a short shifter is often mistaken. In fact, it's a mis-nomer.
a Short shift is physically LONGER.
it's all about leverage points. the shifter has a pivot point roughly 3/4 of the way down towards the linkages or cable depending on the car. simple pyysics will tell you that it takes a shorter throw up top when the bottom is longer.
cutting the top does nothing... if its too tall, cut it, but its still the same distance to each gate.
cutting the bottom makes your shift longer