Well we went back to the drawing board today, and decided to scrap the idea of having both sets of LEDs light up when braking. Instead I ran wire from the left tail light to the right one and spliced it into the working rear fog light. I guess I will now use the fogs all the time now (even though with the xenons I never found that I needed them). Below are the finished product.
Right side Fog and Parking turned on:
Shot of both with fogs on:
Shot of both under braking:
I have to give thanks to Dad in the background, who shares the same passion for his 2003 Boxster that I do for mine. His is on the right: