I used a alum D loop for years...never hit my rest or caused any problum exept a bit of speed loss... ending up At 284 fps I was fine with it.. just sayin. I use a string D loop now But still have the tru nock on my old string..that was not shot out.
I've always worried about those thing cutting strands of the string, something that we've found with tube type peeps. :(
Can you imagine how many times it hits with a shorter brace height!!! Any of this shown with a stringstop installed?
I would use one of those but it would be a lot cheaper to just tie an old razor blade to the string.