If you just cut the shifter, instead of getting a short shifter kit, you would lose levearage and actually make it harder to shift. Plus, you would have to find a way to re-thread, or weld on the threads that you cut off for the knob.
I'm not sure which model 6 you have, but a short shifter for the ms6 is around 150, not 70.
Best reason not to just "cut" your shifter instead of a kit... (ricer)