Reply to Modding X1 Knobs etc

I've scoured the community s for as much info as possible but i wanted to ask some questions that would help me find solid answers.
I would like to modify my Kontrol X1s in a manner similar to this
big props to Deejaysoul for that, since I am ripping that picture from another thread. Anyway, I am under the impression the knob shaft of the X1 is 6.3mm or 1/4th" but I haven't been able to find confirmation on that, but if I am not mistaken the knobs are D-shaped. Now, I treat my controllers very carefully, and am a bit nervous about just yanking the knobs off the controller. How does one go about properly modifying the knobs without screwing anything up?
Also, do the different knobs on the X1 have different shaft sizes?
I would be extremely grateful for guidance and general tips.