You can find the info in CPF but have not seen the pictorial version. So here it goes. Upgrade is pretty easy and straight forward. A Leatherman 3/32 allen bit will be usefull. You can use any allen key too.
And don't forget the McClicky switch..duh.
1. E1e with the McClicky.
2. Z52 Tailcap which is a twisty.
3. Z52 with the McClicky.
4. Use your hand or plier to remove the spring. I used my hand so I won't damage the spring.
5. Insert a 3/32 allen key into the allen screw.
6. Press the rubber boot using your finger tightly while undoing the allen screw. What I did was pressing the rubber boot/switch against a table while undoing the allen screw. It can be really tight.
BTW you won't scratch the tail cap as it's above the rubber boot.
7. Once the allen screw is removed together with the cup, you will see a rubber retainer which hold the rubber boot and a rounded metal piece which keeps the shape of the rubber boot. I used a plier to hold the 2 notches and turn the tail cap to unscrew.
8. Z52 completely disassembled.
9. These parts you keep in case you will need the McClicky for other project. The process of installation is completely reversible.
10. Get the McClicky and rubber boot ready. Press the rubber boot into the tail cap using your finger. Make sure it sits properly.
11. Tighten the McClicky finger tight only. No need to use additional force such as plier. You will spoil it if you were to remove it.
12. Done completely secured in the tail cap. Now you can have a clicky tail cap.
Hope this simple tutorial will help you in upgrading your twisty tail cap.