Recently purchased a clutch stop from Nelson aka bmwclutchstop @ gmail.com and figured I'd snap a few pictures during the process. It's a fairly straight forward install (10 minutes) but it's helpful for someone that doesn't know how or where the clutch stop installs.
Nelson's clutch stop comes with 3 parts. The stop itself, a flat washer and a nut to lock it in place.
In comparison to the stock clutch stop, this one offers more adjustability allowing you to reduce clutch pedal travel. I also had the UUC big boy stop in my M3, but didn't want to spend much on a part that does the same thing.
The stock clutch stop is made out of plastic with a rubber condom.
The stock clutch stop is located on the floor directly behind the clutch pedal. Remove it using a philips screwdriver.
Once removed, it's just a threaded hole. You want to put the flat washer first, then the nut so that it sandwiches the washer in between.
I started with the nut fully threaded down (longest clutch throw) and then adjusted it until my car stopped starting. The clutch has a switch that prevents the car from starting so you can't adjust the clutch stop to the longest setting (shortest clutch throw) without modifying the bracket that holds the pedal switch. This can be easily done by bending the bracket. Or hardwiring it to disable the clutch switch. With the clutch stop in, you simply screw it by hand. Even with the clutch stop at the shortest length, it's noticeably shorter than stock.
Hope this was helpful! Enjoy your new shorter clutch.
Link to clutch stop.