To tighten the nocks up a tad, insert them 90% into the arrow shaft through a piece of plastic grocery bag. Then, trim up to edges with a sharp x-acto knife blade and then push them the rest of the way in. Try this thickness, which has worked for me, and if you need more thickness, use trash bag. If you need it to be thiner, use saran wrap. You can adjust the material and get just them snug enough to rotate with resonable force, but to stay in place while being shot, even if you have a hard surface impact.
Mark