May not have to cut the bottom at all. <div>You might be able to tack the ply insert to a piece of balsa or a bamboo skewer then, using a strong light and holding the fuse near-vertical with the tail down, squeeze a couple drops of slow CA out and let them hit the tail area where the insert will go. Then maneuver the insert into place, let it set a minute or two, then twist  the balsa/bamboo to snap it clean. </div><div>
</div><div>A couple dry runs are suggested so that you can do it before the glue sets up. </div>