What is the best method for drilling the wing attach holes?
The archives are full of discussion on this issue. Consensus is that the plans recommended spot face tool is not adequate for the job. It takes a Loooong time, gets very hot, and dulls quickly. In addition, the excess heat can damage the structure. Various cooling methods are offered including water. One builder even went through a couple of spotfacers before trying a different method. Many suggest using a hole boring tool such as the Morse #TAIO-5/8″ high speed hole saw. Use a 1/4″ pilot hole and a long 1/4″ pilot bit. Be careful to ensure the hole is concentric with the pilot hole. If the holes come out a little large (as much as 0.007″ over) RAF say its ok to fill them with flox and cure while the wing is bolted to the spar. Nat does not like this approach. A popular method is to grind or use light taps with a hammer to make the hole cutting tool bore the correct (smaller) size.
