When I first fit the wings I messed up when I drilled the 1/4″ holes to 3/8″ and glued the RS-401 aluminum bushing in place. It seems difficult to keep the drill perfectly straight. The grain of the wood will push the bit toward the softer areas. So I ended up drillng the holes out to 1/2″ and gluing a dowel in the hole so I can start over.
This time I have a plan to ensure the hole is straight. I took a scrap piece of 2×4 and drilled a 3/8″ hole through it on the drill press. As you can see the aluminum tube fits perfect inside the 3/8″ hole.
After installing the wings and drilling the 1/4″ hole I put the 1/4″ pin in the hole and slid the aluminum tube/2×4 over the pin.
Next the 2×4 was clamped to the rear spar carry through.
The tube and pin were removed and then the 3/8″ hole drilled through the 2×4 into the carry through. The 2×4 held the 3/8″ drill bit perfectly straight. I am much happier with the results now.