The carbon fiber composite plate (shown here) fit the internal fuse opening using a dremel wheel and point cutting bit. A drill was used to mark the shape to remove. Then, round and flat files scoured out the rough edges. At close to an ounce, this plate is several layers CF over birch ply; this is to provide a brace for the wing supports - mostly vertical forces in compression and tension. Use gloves - nitrile or laytex for abrasive work on these composites. For wet epoxy work, use nitrile or industrial butyl gloves to preserve your hands along a mask with OV filters and well ventilated area - at a minimum.
As this plate is the first in a series of structures which must work together to provide adequate load bearing strength, all pieces are first made, fit, then epoxy bonded together.
Actually, at this point, the scope of work is no longer limited to repair but is now modification to fit and bear the higher possible loads from the new wings; both the 8 foot and the 6 foot wings.