By filling the holes in the cowl area I added about 7.2 ounces.

Since this is a light-weight car I couldn't add this weight without cutting some weight too! I cut off the remaining unused brackets and tabs, whipped out the hole saw and managed to trim off 7.2 ounces to counter-act filling the other cowl holes.

Here is the final product:

Expect to see a lot more swiss cheese in the future!