The under camber 50% score cuts on the FliteTest Old Speedster and the Old Fogey wings need to be opened up a bit before gluing. One way to open the score cut up is to use sandpaper. To get a really even sanding job I use this sanding sled. It is easy to make from scraps. Use pairs of triangles for added strength. The box channels on each side help to prevent warping, especially if you use spray adhesive, like 3M, to adhere the sandpaper to the foam board. It works on both the wing center section and the wingtips. Sand both edges, front and back.
Occasionally the slots or servo openings on your foam board models need to be made a bit larger. And it is true for scratch built models or kits. This tool is handy for cleaning up or enlarging those holes. The paint stirring stick can usually be had for free at your local hardware. You may need to trim it a small amount. While you are there pick up a package of self stick sand paper. Use a finer grit, say 150 or 200.