Took some pictures to help clarify a little. I put everything back at stock, then did it again and yes it is quick, easy and easily reversible if you don't like it. Just be sure to hold onto the green grommet.
So first off, here's where you start. The clutch pedal is the one with the red line. Right above that you can barely see the green grommet.
After that is removed:
The piston is behind the clutch. The most frustrating part is lying on your back trying to get this.
The length of the foot doesn't matter much because you're going to remove the excess. What matters more is the diameter of the thread so that it fits in the hole. With the ones we had, we cut 1/4 or about three thread lengths. Here are the measurements of the threaded part (after excess removed)
and compared to the stock plastic grommet
After you insert the foot you add the threaded plastic piece that it comes with and tighten.
Your threads should be flush or a tiny bit protruding from the plastic nut piece.
After that drive and enjoy! The play feels a lot better and keep that green grommet somewhere like the center console in case you want to change it back.