Ingredients from e-tokki (fast shipping):
Sanwa Stick: http://www.etokki.com/Sanwa%20JLF-TP-8Y-SK
Buttons: http://www.etokki.com/image/cache/CWB203C_blue-250x250.JPG
Button Wiring: http://www.etokki.com/Paewang%20Button%20Harness
Spacers: http://www.etokki.com/Crown%20CWB203C%20spacer
Screws (4x): http://www.etokki.com/MiscParts/Short%20Screw
I’m making this thread because this is the information I was looking for when I wanted to mod a Datel stick for the first time. The photos are taken with my phone, sorry about the poor quality. The JLF-H wiring was included with the stick, and I recommend using it instead of the custom wiring harness shown in the popular mayflash mod. I tried both, but this solution is easier and safer for your stick.
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First off, beginners NEED to read this:
[LIST=1]
[*]When soldering, wear thin gloves and cover your arms.
[]If you use solder which was directly applied to the soldering iron, the flux will be burnt off and it’ll be difficult to make the solder cling to the joint or microchip. Solution: Hold the soldering iron behind the wire and gently tap the solder towards the wire on the other side, the solder will melt “through” the wire towards the heat source and cover the wire or joint, without burning the flux.
[]Apply small amounts of solder on both joints before attempting to connect them.
[/LIST]
Tools: Soldering Iron, solder for electronics, screwdriver, x-acto or industry knife, scissors.
Unscrew and remove everything, except the circuit board (PCB) connected to the PC/Xbox wire.
Be careful not to hurt the main circuit board when breaking off the connectors to the button PCB.
Push the CWB203C buttons in place, facing the same way. Use spacers and make sure they’re tightly secured.
Use scissors or a knife to cut off the ends of the wires, then peel off some plastic at the end to expose the wire. (ignore the sanwa stick in the background, we’re using the JLF-H istead.)
Disassemble the stick and remove the heightened areas where the screws go. Reassemble it with the connector (where you plug in the JLF wire) pointing to the right, when the stick is up side down.
The screws from e-tokki should fit perfectly and allow you to fasten the transparent plastic part of the joystick.
Soldering:
Unscrew and remove the circuit board. Solder the button harness to the circuit board, make sure none of the connections overlap. The black wires (ground) should be on the RIGHT side of the harness. Solder the JLF-H wires to the PBC, as shown in the picture, this is different from the wires used in any other tutorial, and the most important part of this tutorial.
Place the fully soldered PCB back where you found it. Put some solder on all the wires on the buttons, and solder them in place.
Black wires at the bottom of each button, colored wires on the right.
Use the legend below to see which wire should go where.
http://img97.imageshack.us/img97/7131/pcbbuttonlayout.png
Put the PCB back in place and connect the JLF-H wire to the joystick.
That’s it! All the buttons and the stick work perfectly. This took about six hours in total.
Note that this is a guide for beginners, I realize some may see this as simple stuff. Hopefully this can help some of you avoid hours of work. I expect my next stick to take half as long, with the experience I gained from doing this. 
