I think I recall that Ben tried shortening the height of his factory shift knob:
Ball bearing short shifter !
I personally love the stock knob height (combined with the modestly shorter throw of the 997 shift mechanism I installed) on my 5-speed 2001 Boxster. When I tried temporarily running with a lower positioned, duct tape ball shift knob for a while (necessary for me to keep driving the car while refinishing my shift knob/boot), I found it hard to get into gear sometimes due to inadequate leverage. The conclusion for me is that shorter throws are not necessarily better.