I've just ordered a cnc machined rc transmitter balancer. It turned out that the orientation was 90deg off :-) as i liked the cnc finish of the balancer i just thought i could turn the ring.
So here is a step by step tutorial of how you can turn your ring on a Graupner MX-20. As the other Graupner MX transmitters share more or less the design i believe this should also work for an MX-12/16.
1. Open the battery compartment and take out the battery, take out the six screws holding the transmitter together.
2. Pull the case apart. It should go very easy. Disconnect the antenna and take out the 2 screws holding the antenna module. Flip the antenna module towards the white cable out of the way.
3. Unscrew the 4 tiny screws holding the base board in place. I did this to have a little more room to take out the board under the antenna module i will call this switch board from now.
4. Take out the 4 screws holding the two switches, then unscrew the 2 screws holding the switch board in place.
5. Lift the board a little bit and gently press out the two switches.
6. With the cables connected you cannot take out the switch board completely. But lift it enough so you can loosen the 7mm nut from the ring.
7. Take this ring thing and file a flat surface from about 2mm x 8mm 90 deg from the other flat surfaces.
8. Check the distance of the two surfaces. This should be about 11.5mm.
9. Check the fitment in the transmitter it should be a tight fit, otherwise it could have some play.
10. Once you are happy with the fitment you can assemble the transmitter back together. The procedure is just vice versa. Make sure you don't forget the antenna plug. Now you can mount your transmitter balancer to the transmitter.