I agree. I've been on plenty of foot chases and broken up plenty of fights whilst wearing my custodian and it's never come off. If it does then it probably means the officer is wearing the wrong size.
I think there might be quite a few officers with the wrong size custodian on....I felt that mine didnt fit correctly
(bit too big) when I got it fitted at hendon, but I'm yet to start training so it might be ok once I'm attested and my heads got a bit bigger ha ha