Hi guys, I’ve been working through the fluting of the ribs and drilling of the counterweight for the flaperons. A military sheet metal guy gave me this technique that I want to share with everyone (I’ve seen many different techniques to include marking the holes and drilling on a drill press). This works well and makes clean holes without elongating the skin holes. Use a drill bushing #30, a drill bushing housing, 2.75 inch number 30 drill bit and two layers of painters tape to protect the skin. I used oil on the drill bit and also a slow speed to drill the holes. Have a few drill bits at the ready, the stainless dulls the bits fairly quickly.