If this is a top mounted wing, drill the hole in the bulkhead slightly lower than you think it needs to be. Then, by trial and error, slowly enlarge the hole upward until the wing slips in. The open area in the hole below will not hurt anything and will aid in mounting the wing later as the wing can be at slight angle when you insert the dowels. If a lower wing, drill the first hole slightly higher than you think it should be and do the same trial and error enlarging the hole downward until things fit.