It was done by hand! That's amazing. It took about an hour to finish using an electric sander, a flat file, and a 3mm drill. There are two slots at the front and back. The seat post is firmly fixed in place using carbon paste.Yes the dropper post is 40mm+ too long in most of the E82 sizes. Did you find any quick and easy ways to cut it down? I'm looking to do the same myself. Another friend did it with too many hours of hand sanding/grinding.