For cdalefan and danredwing:
Sorry it took so long to reply here. I had to hunt down the bike's "Baby Pics". This is from the first or second day of ownership.
This is how the cable was originally routed. Not quite an S-bend at this time, but you'll note the strain due to the tight bends at the cable stop and at the rubber boot where the housing enters the caliper.
This configuration lasted about a week. The return spring just didn't cut it. The brake was dragging all the time. It was at this first reconfig that a longer piece of housing was installed, and that introduced the S-bend mushiness, while resolving the dragging.
As for the slack, Dan, that can be taken up at the caliper. My guess is that your actuator lever is closer to noon or one-o'clock rather than 11:30 as in this pic, or 11 o'clock as it is now on my bike. In other words, the brake is always in partial actuation. Back out the adjusters to compensate.
Later I had to reroute the cable entirely to clear my cyclocross tires. The bare section from under the BB to the that cable stop on the bottom of the chainstay cut into the wheel area a bit. Strangely, my 35mm Nokian studded snows cleared the cable, but my 34mm Bontrager Jones CXR tires would rub the bare cable.
It was at this reconfig (after several iterations) that I ran the cable in housing for the full length, right from the lever. That eliminated the S-bend mushiness, keep the cable out of the tire space, and did not re-introduce the dragging it had when new.
This pic is of the second-last reconfig, shown here parked outside my bank (in a snowbank) with the Nokians mounted and the stainless-steel rotors on my winter wheelset.
Here the housing extends to beneath the BB. As you can see, it picked up all sorts of gunk there and there wasn't really a good place to anchor the end of the housing. It bobbed up and down with actuation. That re-introduced some mushiness. The housing now extends all the way to the stop just above the T in Trek.
Cdalefan, you'll see how I now have wireless speed and cadence sensors mounted on the chainstay. There's hope for you and your Garmin yet.
Hope this helps!