Unless you are using those plastic berry baskets to divide your hatching tray (to keep marked eggs separate or something) I wouldn't introduce anything at "lock down." No rings, no paper towels, etc. They could get in the way or prevent a chick struggling in the shell from getting to a good position to hatch. The eggs do move around under a hen during hatching, they just might not be able to roll as far as they can in a spacious incubator. Good luck with your hatch! Once the majority of your chicks have hatched and dried, you might want to remove them if the incubator is so crowded that the hatchlings are pushing the not-quite-hatched eggs around. Take out the eggshells, too- I had one chick get stuck inside of another chick's empty shell because it rolled onto the end of a pipped egg like a cap!
