I bought parts with the intention to mount it, but I ended up selling the parts. My plan was to thread the EW-JC130 y-split with a EW-JC 200 inside the handlebar, with a 1100mm (?) EW-50 cable going from the EW-JC200 inside the handlebar and to the SM-JC41 port in front of the cranks. If you need blutooth you can change the EW-JC200 with EW-WU111 connector.
As i said I ended up selling the parts. I like the simplisity of the original setup and i did'nt want to risk ratteling in the handlebar. I also did'nt want to thread everything and bleed the brakes one more time. I can not confirm that this setup actually works. I believe it can be difficult to thread the connectors through the bend in the handlebar. I dont think it will work with the brake cables mounted.
In the original setup there is a free port in the right shifter. The easiest solution might be to add just one of the SW-R9150 shifters to the right shifter for gearing down. Not perfect, but it might help in a sprint.