Next glue former F4A on top of F4B. F4A has a hole sized for the battery tray, and F4B has a hole sized for the servo tray that goes under the wing. Take the paper off of the skin labeled F3-F4, shape the skin and glue the ends together. Temporarily separate the nose section off of the battery tray. Attach skin F3-F4 to formers F3B/F3C, making sure that the skin is a flush fit to the front of F3B. Make sure the skin is turned the right way and not facing towards the nose of the plane that you just slid off of the battery tray. Once the skin is attached and glued, slide on the F4A/F4B former assembly, with F4A side facing the front of the plane and mating with the end of the battery tray. Only F4A should fit into skin F3-F4. A lip is formed by F4B for attaching the next skin.