Di2 onto retro steel frame.

[EddieJT]

I'm planning on doing the above. The first obvious problem is getting the 5mm cables to pass into the frame; do redundant/empty downtube shifter bosses leave a hole that passes into the frame that a di2 cable could be threaded through?

I'd need one hole at the front near headtube, and one at the rear (1x11 setup, so no front derailleur). If I did have to resort to drilling, what locations would least compromise frame integrity?

 

[Pionir]

Have you considered the SRAM equivalent? I believe it's all wireless so might be easier to fit.

 

[EddieJT]

Think I've duplicated this thread somewhere else.

Anyway, yes I know of eTap, but I already have the di2 which I cobbled together second hand and modified. It's cost me a fraction of what eTap costs.

This is tempting me though: http://xshifter.com/