[patrickt]

bb -- any chance you could post some actual pics of your bridging? If you've done it correctly (and it sounds like you have), and the four ways only come on when you're also pushing the brakes, then the only thing I can think of is that it's a peculiarity with the circuitry of the trailer relay itself. If that's the case, then you could roll the dice and include the red wire on the trailer relay in the bridging and just see what happens. That should work if standing on the brakes work, but you won't know until you try it. If it does, then you'll need two switches to connect the three wires so that you disconnect all of them from each other when you're not flashing.