I got everything installed and tested on my 2009 C14ABS...but am having a heck of a time trying to figure out where to run the wire for the brake relay under the seat to the rostra unit.  I mounted the rostra unit underneath the right nose of the bike...on the ram air duct.

Any advice?

You can pick up the brake wire to trigger the relay at the front of the bike, off of the front brake lever harness. Been too long so I don't remember the color. No reason to run it to the rear of the bike.

My experience is from a '10 model but I think it will apply to a 2009 model. As Flathead says, you can find a brake
wire in the front bundle and just find a spot in the front for your relay. OR..as Fred mentioned to you on the other forum, you
can run it under the gas tank. There is no need to entirely remove the tank, just remove the four tank bolts and stick a small board or something under it in the front and lift it in the back by hand as you run your wire rearward.