Ok Guys, finally I manage to get some pictures here.
Sorry they are rather unclear, I do not have my camera so I use my psp cam.

so here is my CH HOTAS :

Sorry I miss the Pro Throttle, it is still under the table.
I have use this since the 90s, so now it is almost 20 years.

here is the inside part:

this is used to be a gameport joystick,
I have made it USB by using mjoy16, thanks to Sokol1. cheers

here is the hall sensor and the magnets:

I glued the magnet to a unused pots part, and put the sensor above the magnet.

The magnet is very near, but does not touch the sensor.

Sokol1, with A1302 there is no need for shielding the magnet, mine works just fine.

Gene is right, after you know what to do, hall sensor is very easy to make. copter