Per the plans, clecoed all of the vertical stablizer together to get the initial fitment and match drill the front four holes to the top and bottom ribs. I used clecos in every hole to make sure everything was lined up and nothing was forced. If the ribs do not fit, make sure they are formed to mate to the skin well. Vans does a wonderful job of machining the parts. I never had an RC Plane that went together this well.