Completed my install yesterday. Grinding down the top of the zhp knob wasn't as bad as I thought. I used my drummel with a die grinder. I flattened the entire center part. Drilling was the scariest part. I ended up breaking the first drill bit. Second attempt was better. I drilled at the 1 o'clock position when looking down at the knob.
After that it was easy. I took all the blue tape off (used to protect the leather) and wiped down the knob. Next I placed in the led board, then the black ring to hold the board in place and finally the cap. Everything fit perfectly I didn't have to use any glue.
Thanks so much for this DIY. I love the feel of the new knob!