[//TMT]

What a great hack! I am doing this asap.

Some observations:
- looks like you can code the left and right rears individually
- looks like both bulbs are already installed (!)

In the Volvo, only one bulb is installed, on the driver's side. This is intentional, and that bulb is somewhat brighter than normal. From your photo it doesn't look like they're brighter on ours? OTOH, that code says "PWM", pulse width modulation, so perhaps increasing/decreasing that coding will also tweak the brightness.

I like the rear fog in my Volvos for visibility, but it has one magical side effect - the car behind immediately drops back. It's extra-safe in fog, but I sometimes use it anyway. I think it's the bright, asymmetric look that makes it work.

The only drawback of a single light is that sometimes people report they get pulled over for a defective taillight. Has not happened to me.