For those interested in adding a flap position sensor to a RV-12 ULS setup with the Garmin G3X, here's how I did it:
1. Purchase a Ray Allen position sensor. I used the POS-12, but you could use any of them. The difference with them is how far the "throw" of the sensor arm extends.
2. Fabricate a hat bracket to mount the position sensor. I added nutplates so that the position sensor could be easily serviced. Also fabricate an extension arm with a 90 degree twist. The length of the extension arm, and the height of the hat bracket will depend on the position sensor you use and the related "throw" of the sensor arm. Here's what mine looked like:
3. Attach the hat bracket to the seat rib that is to the right of the flaperon mixer arm. Attach the twisted extension arm to the flaperon mixer arm. Attach the position sensor to the hat bracket. Connect the position sensor to the twisted flaperon mixer arm extension with remote control airplane flight control rod and servo arm hardware. It should look something like this:
***The key to the entire installation is to ensure that the throw of the connection to the flaperon mixer arm matches the distance that the arm of the position sensor extends. ***
4. Wire the position sensor. I grounded the blue wire coming off of the position sensor to a bolt on a seat rib, then connected the orange wire to pin 30 on the P244 bus on the GEA 24 and the green wire to pin 31 on the P244 bus on the GEA 24; see Figure 30-2.3 for the flap position sensor wiring example in the G3X Touch Install Manual. Calibrate the switch on the POS 5 discrete input per section 220.127.116.11.1. of the install manual, which is similar to how you calibrated the trim sensor on the original G3X Touch setup.
4. Unfortunately, Garmin does not have a way to link a master caution for flap overspeed if the flaps are deployed above 82 kts. Hopefully, that is something they will consider in a future update.