I have the older Tri-Bar, installed it back when the bike was still fairly new.
I added LED replacement bulbs to the rear turn signals then put in the HD Run//Turn/Brake module.
The turns flashed OK for a little while then started going too fast.
But I wasn't happy because I wanted the same thing you did, a Turn/Brake only setup.

Then I found a writeup in the Touring section on how to rewire the module to eliminate the run function.
I did that a year or so ago and it even cured the fast blinking.
Now I can't swear to it, but I thought everything was working fine until a buddy of mine who happend to be riding behind me earlier this summer noticed that if I had one of the turn signals on along with the brake everything was fine.
But if I let off the brake or just hit the turn signal button the Tri-Bar blinks along with the turn signal.

The strange part is that I'm not all that sure I want to figure out what's wrong and fix it.
Call me a crazy if you like, but I kind of like the idea of having another (and bigger) light blinking when I'm turning instead of just the little turn signal.