Wood dowels will be used for mounting the control horns, the position is laid out and 1/8" lite ply plates are inset to provide additional support for the dowel on the top and bottom of the core. I made a jig for the Dremel router for this purpose, the plates are glued during vacuum bagging. The hole is drill after the skins are glued on. I got his idea for Mike Hurley's project Extra 300 in Model Aviation.