Dave-
I installed a Stay-in-Play Duo in our 2009 Honda Fit Sport. It is a great system; prep takes only a few minutes, and even that is due to Honda's procedure (consult the manual).
That said, the Duo installation in the Fit was no walk in the park:
1) Limited space to install the system unit
2) Getting actuator air line through firewall
3) Getting control box wiring through firewall
4) Attaching the actuator cylinder cable
5) Mounting the breakaway switch
I did the brake light installation at the same time, so there were more wires to run. I also added several connectors so I could replace components without cutting wires.
I could pull the system unit, control box, actuator cylinder and breakaway switch in under two hours. I'd have to plug the vacuum line, rather than remove it. I would not remove the air line or the rest of the wiring.
It's more likely we'll sell the car to someone who wants a working toad, rather than pull out the equipment listed above.
We use a Roadmaster Sterling towbar and installed a Roadmaster baseplate.
Our Fit is a nice small car, and an easy tow at under 3,000 pounds. I'd be happy to share the details of our Fit's Duo/brake light installation. Just drop me a private message with your e-mail address and any questions.
By the way, there is a tow brake design midway between the Duo and the "bowling-ball bag" drop-in, and that is the NSA
ReadyBrake and
ReadyBrute towbar. They are mechanical systems. The biggest problem (as I see it) with installation in a 2009 Fit would be finding a path for the cable. There is almost no room in front of the brake pedal arm to go through the firewall, as the power brake parts are located in that area. Worth a look, and perhaps a call to NSA, though.