I replied to your other thread too, but if you are set on using the Nockturnals I would try and find some practice nocks that weigh the same.

When I was shooting firenocks they included practice nocks that weighed the same as the actual firenock.

Adding 10 grains on the one arrow will make it fly different than the lighter arrows.

I really liked the firenocks, but have since switched to blaze orange fobs with a fluorescent orange arrow wrap, it sticks out about as much as the firenocks did.