One suggestion: Insert the cable into the casing as you position tape the casing before adding the handlebar tape. I just positioned the casing, minus the cable, and then re-taped the bars. While I was doing this I also added Suntour barend shifters with the cables routed under the tape to the stem, so I was routing four sets under the tape.

Since it was the beginning of winter, and the Traveler was on the trainer for the next several months, I had thrown a set of cable-free bullhorns on the bike. My newly levered, casing, and taped bars were set aside for winter hibernation (minus the cables running through the casings). At the end of March, when it came time to take the Traveler out for it's first spring ride, I sarted to add the cables, and with the Tekro brake levers, I had a bear of a time inserting the cable into the casing. I succeeded, but it took hours instead of a few minutes. Needless to say, this experience tested my usual calm nature.