Only had to drill 2 new holes in the Matrix. I used the existing license plate holes for the center support.
Materials to start:
Cut a piece of L-Bracket the same width as the license plate:
You'll notice in the previous picture that I put the bolts in from the back of the Matrix. Thats so I could use the remaining bolt length for mounting my license plate without actually using the license plate as a load bearing component:
I ended up having to cut two slots in the bracket for where the bolts for the lights will come through. Painted it black with a hammered finish.
Then I mounted the Thule bar. Leveled everything the best I could. Then drilled two more holes, one through each 4xG upright and put a 1/4-20 bolt through each. This last step made the light bar as sturdy as can be. It's now one "solid" piece with the 4xG.