If the shifter shaft is really long like the Spark's, you can easily hack off 4 or 5 inches like I did. A few minutes with a hack saw is all it takes, just make sure you figure out what is comfortable for you beforehand. My son's arms are a little shorter than mine so he cut off about an inch less.
Those aftermarket knobs come with a set of plastic collars for a tight fit on the shaft, the three Allen head set screws keep it very secure. I was able to find a knob that looked very much like stock for less than $10 at the auto parts store. It only takes a few minutes to swap out any knob that suits one's fancy. I wouldn't worry about losing the threaded part of shaft, it's just a cheap and secure way for Mitsubishi to attach the stock knob.