Can you be more specific?
I did mine the same way as Sam and Steve. I found it far more secure than the fishermans knob method
I know of a double-fatality in which a perma-bungeed necklace directly contributed towards the incident chain in a technical penetration dive. The nature of this was confirmed by those involved in the body recovery of the two divers concerned. It hasn't been confirmed in a formal incident report yet, because no such report has been forthcoming from the local authorities. If/when it is, I suspect the report will draw heavily on the
expert advice of the divers concerned with the recovery and those who dive the site concerned regularly. I've dived that site frequently (350+ dives there) - and was filming in and around the location of the incident last week.
Now... I'm not saying the perma-bungeed necklace "killed" anyone... just that it was a significant factor in a chain of events. As a factor in that chain - a different configuration approach would have possibly led to a more favourable outcome. The incident concerned involved technical penetration into a confined environment and the bungee was the cause on an entanglement issue.
I don't want to side-track this thread into an A&I debate... and I hope you can understand my refusal to quote specific details. That refusal doesn't stem from lack of knowledge, but rather an ethical obligation towards the friends/family and co-workers of the deceased, coupled with legal considerations associated with the still pending accident report. I'm sorry if that quashes anyone's idle speculation into a fatal incident.
To generalise this issue - most experienced/technical divers understand the relationship between 'break-away' attachments and the risk of entanglement. If such a diver chose to apply this principle to any area of their configuration, then I'd suggest that equipment stowed around/attached to the neck is a primary candidate for such an approach.
I don't have a pic of my configuration - because my kit is stored 3 hours travel away at this time. However, it is of a very similar configuration to that posted by Halocline... using 2 sliding knots to create an over-lap loop for the mouthpiece. Once adjusted for size, those sliding knots are fixed with zip-ties. It is just as secure as a perma-necklace, but allows the regulator to be freed with direct manipulation, without the need for cutting anything. I use the same approach on my single, double and sidemount reg configurations. I also build one of these for every student I teach, recreational and technical.