Di2 set-up question

Here's a bonus tip for you. When routing your cables wether its inside your frame or handle bars. Use a vacuum cleaner, gaffers tape and dental floss (I recommend mint flavoured). Tape up all holes except the ones you are routing through, suck the dental floss through using the vacuum cleaner, then tie the dental floss to the Di2 cable and pull through. Sometimes a bit of tape is needed around the connector to pull evenly through.

If you have a Garmin (810 or later) then you can use the hood buttons to changes pages set other functions on your head unit. Google will show you how.

Good luck with your bike build.

I have exactly the same set-up and went with a small EW-JC200 2-port through junction where the short 50mm part of the EW-JC130 exits the bars in the centre. The hole in my Specialized Aerofly bars was big enough that it tucks inside nicely keeping it nice and clean.

I do have a EW-WU101 for ANT+/Bluetooth but it's tucked in the bottom bracket area with the SM-JC41.

As others have said the wireless connectivity is very useful and if the EW-WU111 fits into your set-up then it's well worth a look.

To hit on what Jonni said, you can still run firmware updates and (if compatible) invoke synchro shift with a pc connection. But seriously, the connectivity you get with the wireless unit is sensational. It's worth it for the battery level indication alone, and that was the main reason I shelled out for it. If that sounds like something Shimano should have in there as standard, that's because it is. I have a couple of colleagues with the hydro shifters, and they have three plugs in each one. Makes it incredibly flexible.

Wow, I think I need to either do some studying or be content with analogue!! Now I know how my Dad feels when I send him a whatsapp!!

So the R9150 levers have 3 ports for all the extra switches for the pros

I think the new iteration (ST-R9170) may offer three ports each.

At least from what I can see on the schematics in this document.

http://si.shimano.com/pdfs/dm/DM-R9150-05-ENG.pdf

I would still double check that before purchasing. 

But, good to know CXR94Di2

There is only one connection on hydraulic Sti Di2 road lever. You get more on non hydraulic levers

You have two if not three cable ports on each STI lever. You can simply run a cable from one lever to the other and then back out again to the junction box. All the cable length seem to sell for the same price. So just get a longer cable from one of your levers.

I've recently converted to the new handlebar port. I was advised not to drill my handle bars by a carbon specialist (who have previously drilled multiple holes in my frame). Pro make a set of Di2 ready handle bars. I'm quite happy with the new bars and the visible absence of Di2 cables.

I like the wireless unit. It makes setup easier as you can simply do it from your phone instead of a computer. It also connects nicely to my Garmin, giving me percentage based battery status, shift mode status and gear ratios - maybe all nice to have but once you get used to it you wonder how you could do without it. The big bonus is the ability to control both lights and Garmin head unit from the Di2 buttons on top of the hoods. Those buttons are only found on the Dura Ace levers and the latest iteration of Ultegra and the latest iteration of the hydraulic levers (those with a rubber cover on top - I think they're called ST-R9170).

I have a mix and match Di2 XT and road shifters. Ive just ordered a the Mt800 display to allow synchro shift. I run a 44-28 chainset with a 11-40 Cass for mountain climbing. Love the ease of Di2 adjustment

You could use and extra' junction box B' further up the  downtube or handlebars to allow all connections, quite cheap considering Di2 cost overall.  Those handlebar ports are expensive!