I just assumed that you don’t need the STIs because the TT shifters work on their own, AFAIK.
Also, isn’t there a 3port and a 5 port version of the front harness? What good would that do if you couldn’t plug in stuff?
I guess you could even look at Alfine shifters as well.
I’m sorry I don’t have a definitive answer for you, but I hope those leads help you find the answer. If you do, I’d actually like to know, maybe you find the time to report back.
Fairwheel Bikes and its Authors