This set up is better for me in 11 / 28.The circuit is now much quieter and much more fun. In 11/40 I did not need the last 3 pinion.
Yes I install himself and no difficulties and yes is the shimano di2 battery.
I have changed Dura-Ace crank with bottom bracket, rear derailleur ultegra RD 6700 and Dura-Ace cassette cs7900 10fach with chain. The price with Di2 ca 800€
Where do you have the battery mounted? Can you take a picture of that please? I went ahead and ordered the XTR Di2 so I can keep my existing chain and cassette....for now.