there is enough room...
I'm doing exactly the same - fabricating a bracket of out aluminum to hold the plate, then I'm either mounting short stalks next to plate or better, I'm probably going to the oval flush mounts on the underside of the eurotail (like those pic posts from a few adys back- nice work BTW)
I don't think the LED array in the tail section makes sense - you need too many LEDs to make it bright enough in the day. In any event, I'm confident that there will be enough room to mount short stalks next to the plate. Anyhow, since you are making your own bracket anyway, you could always move the signals up or down on the braket if you wanted to change the look or fit it differently. I myself like the flushmounts under the tail on the sides!