Regulator Necklace Setup

[ink]

I'm looking to switch to a hog setup with primary donate. I bought a necklace, but how do I actually attach it to my regulator? How do I measure what the ideal length is?
Also, what do I do with the clip for my new extra-long primary reg tube? Why do I need a clip? The videos I found made it look like I just wrap it under my arm and around my neck, so why would I clip it?

 

[Rilelen]

I have a bungee necklace but prefer (and often “steal”) my buddy’s silicone one.

 

[gmerick]

Make sure there are no hard or sharp pieces on the necklace. If you end up in an "involuntary donate" situation while breathing the necklaced reg, the necklace will snap back quite smartly into your face.
For myself, I use a double necklace -- I tied both necklaces with a fisherman's knot, and threaded both necklaces through an old tank o-ring before tying. diving sidemount, this avoids some of the fiddle-faddle with clipping off the long-hose reg.