There are three things to think about. You have the wiring (turn signals / lighting / horn / radio controls / start / stop). The fly by wire throttle (6 additional wires-seperate from the other wiring) and the cables (clutch and Ft. brake).
I went with a 10 rise bar and could stay with the stock wires and cables (almost). For some reason, I could not get enough extra slack for the loom going up the LH bar. I had bought an extension kit just in case, so I ended up using it for that side only. I played around with re routing the loom inside the faring but couldn't find the needed extra length? The Ft. brake cable was tight too, but some creative re routing along the frame backbone found me a couple inches more length.
This was on a 2012 CVO Streetglide. If I had gone to a 12inch rise, I would have needed the extensions all around for sure. I routed all my wires internally like stock (the cables are still external). Make sure the guys saying you don't need extensions for the 12 inchers aren't just running the wires externally.