Jeff, why did you choose the NF rings, and did you need to lap them?
In using NF steel rings, I have never had a scope slip, never had a ring break, and never had the screws back out or come loose. The NF steel rings are the only ones I can say that about. I never had to lap NF rings.
The NF Ultralights, which are aluminum, are still new to me, and I only have a few hundred rounds with them. They allowed to the scope to slip initially, but once I applied some two-sided tape to the inside, they work fine. We'll see how they do for the long haul.