I just did the double DIN radio installation. It is easy on the EUDM as the i88 connector is the same as the JDM one. No need of an adaptator. Just plug it in. I tried to keep the steering wheel controls using an Axxess interface but failed. It recognises automaticaly the wiring to the car (pin 19 of the 20-pinned connector to the Axxess box, pin 20 to the ground) and the Alpine radio, but forces the volume up to the max without me pressing any button. I tried to programm it manually, but it never recognises the volume up button, the first one to programm, when I press it. I even tried with the pins 12 and 11 respectively as I was not sure that I looked at the 20-pinned connector the right way. I gave up
I also connected an amp placed under the passenger seat. Wiring was easy passing the battery wire through the gum of an harness behind the glove box then along the passenger door.
The stock radio/AC unit using the single zone AC control :
The JDM single zone AC control :
The only adaptator you will need for the EUDM is an ISO -> 14-pinned Subaru connector. The harness on the right (Alpine -> ISO) comes with the radio.
I put a pic here but I still need to work on the fitment to eliminate some gapes. It was late yesterday evening...