I used the NF Ultralights with a pic rail for the last two years quite a bit including on a 260, 308, and a 300 Win Mag. Overall, they have worked well, and have proven reliable. Initially, they did allow for slipping. Some two-sided Scotch on the inside fixed the problem and they have been great ever since. Definitely would recommend them if weight reduction is the goal. Use a torque wrench with any aluminum ring to avoid cracking. The NF steel rings are my favorites if weight is less of a concern. The steel have never allowed slipping, and never had a single issue despite many miles of use.
Application of the two-sided tape.
End result on a 300 Win Mag.