If I understand what you are asking correctly, let me try and explain. If you shorten the height above the pivot on any shift level, you will achieve a shorter throw between gears. You can also acomplish this "moving the pivot up" on the shaft, and using a slightly longer overall length lever. This is how the STi STS is about the same height as stock, but has a shorter throw. By shortening the height even further on the STi STS, cutting it down by 35mm, will shorten throw between gears even more, but increase the effort required to move the level throught the synchros.
OK now this make sense. I did not realise you could change the pivot point. i.e. make the bottom link longer on the STi STS.
Without buying a new lever, or shifter, you cannot decrease throw length by adding more distance between the pivot and linkage attachment. You can, however, decrease throw by cutting the top part down a small amount as this mod desribes.
This also make sense. I did not think the lower link length could be changed on a stock shifter. Only the top, by cutting. i.e. shorter throw and slight increase in effort. (what I am considering)
You could also buy Cobb's STS, which allows you to adjust both the height of the lever, and the shift throw distance independant of each other:
But, it's $135, and this mod is free!