Since I had decided to substitute the Dynon pitot tube in the same general area as where Vans recommends for their pitot tube, I went ahead with cutting of the hole in the skin for it. Using the paper template, I punched the centers of the holes and then used a step drill to enlarge the larger radius of the main oval hole. Then I drilled a number of smaller holes along the inside lines of the main oval hole, then used a wire snip to break out the middle, and a rounded file to refine the shape to my traced line. After a few more refinements with the file, I got the opening just large enough to allow the pitot tube to fit in.
I used cleco clamps to hold the pitot tube together with the skin and started match drilling the three pre-existing holes in the skin. Then I used my center-punched markers to drill all of new holes that surround the pitot tube. A test fitting of the skin and pitot tube on the wing confirmed that it fit perfectly.
What's next? Time to scuff, dimple, and prime these bottom wing skins.