I made an inexpensive little jig for checking my Cg. Its just a scrap piece of 2x6 with two oversized kinder-garten type pencils dropped into two holes drilled near the sides. Just enough room for the fusalage of a .40 size plane to fit between with an inch or so to spare. Round off the edges of the erasers a little and they work pretty good for resting the wings on without damaging the covering.