After the build.

This, how to, question has been asked before. In my case I build the airplane, then do a CG check for servo n equipment placement. Then I cut the holes. Thought I’d post how I do it. First you make your tool,a sharpened tube with kerfs cut in the sharpened end. Then I use masking tape to tape the non cutting end for padding for my thumb. Locking pliers to hold the tube.

I use a straight edge to mark the run on top of the ribs. I measure how far down I want the hole. I hold the tube against the rib with my thumb and hold the rib with my fingers or a piece of plywood against the rib. With my other hand I rotate the pliers back and forth. Thumb controls the pressure against the rib and also alignment. It takes less than a minute to cut a hole. A paper tube can be added if desired.