Most of the titanium and steel bikes using Di2 have to be externally wired. While this is not a particularly hard procedure, and the external battery is probably superior to the internal one, Choosing the correct length wires is something of a measure, buy and try situation. I would guess that a shop that does much of Di2 would have a stock of wires and enough experience to be able to guess at the correct sizes to begin with. It turned out that I underestimated the length of the under bar junction to the under bottom bracket terminal block and the length of the BB terminal block to the rear derailleur by a little. So I used the downtube wire to go to the rear derailleur It has maybe 10 cm too long but that is fine. I ordered a longer downtube wire and a wire cover kit since I seem to have misplaced the one I already used part of for the Redline that I sold. What do you want to bet that as soon as I get the new one and install it I will find the remainder of the old kit? Being somewhat of an artist I also ordered some special paint that will match the starflake metallic paint on the bike. I don't expect a perfect match but close enough that you wouldn't notice it without close observation. The rear derailleur wire only needs a short length that is hidden beneath the chain stay, so that doesn't need any matching.

Thankfully you only have to wire these bikes once. Unlike cables which are a bear to replace properly all the time this is nothing more than an electrical contact that doesn't require exact adjustment.

And I'm thinking of replacing the Madone almost new Dura Ace manual group with Di2. This will require me to cut holes in the frame So I'm still thinking about it. I didn't do this before because I had the idea that the frame holes were reinforced in the area of these feeds but looking at the Emonda that doesn't seem to be the case. I think they have a template and just use a Dremel. Or I might sell the Madone off and replace it with a disk brake frame.