Di2 Ultegra Question 1×11 with a set of satellite buttons…?

Hi, I’m looking at building up a CX bike with a 1×11 Di2 setup. Can I use the 3 port junction box (SM-EW90-A 3-Port Junction) with only 1 set of satellite button (SHIMANO Di2 SW-R600 ) connected?

If so do they come with a bung to cover the unused hole in the junction box or can you buy these separately? Also will this work ok with Ultegra 11 speed rear derailleur (RD-6870-GS)

Certainly was the case with 6770 that the ‘brain’ was in the front mech, so you had to use it, wasn’t the case with Dura Ace, so don’t know if they’ve changed it for 6870.

Yup – it’ll work fine. You may need the update using the connector cable.

No bungs available

Bungs part number = 6VE 1500

Shimano call them a “dummy plug”

thanks for your help!