I don't know. The whole setup is relatively new to me. Some people choose to loop the SPG behind the 1st stage which would create a little bit looser bend. This way is a little easier for me to see. It's a MiFlex hose so maybe I can get away with bending it a little more than a rubber one.
My deco bottle reg set came with a gauge setup like that. I used it for a while and then replaced it with a good 1" button gauge.
Mini-SPG, { 1 in | 2.5 cm } Face
I like that setup a lot better.
Just watched video from pool session yesterday. Holy crap! My octo was out of the holder a ton of the time. I just ordered a necklace from DRIS to pick up when I get my Halcyon wing back from the inflator repair.
I use one of these around the neck of my deco cylinder to hold the 2nd stage. I think it was $1.50 at my LDS.
Amazon.com : 50 Silicone Scuba Octo Holder Strap - Made in Maine, USA - Yellow : Sports & Outdoors
It keeps the mouthpiece tucked in, pointing at the valve and overall more streamlined. Never yet had the 2nd stage fall out by accident. And it's easy to see and grab to put the 2nd stage back in if I use it then need to stow it during the dive (so far, only something to do in training).
Regarding your bungee necklace, you can easily make your own with a piece of shock cord (aka bungee). One reason you might want to is that size does matter. You don't want your alternate held TOO close to you neck. But, ideally it would be close enough that you could get your reg in your mouth without using your hands if you had to. It looks to me like a lot of the pre-made bungee necklaces are made big enough to work even on really big people, so they let the alternate 2nd stage hang too low on most people.
I've seen two different methods for making a bungee necklace. One is to tie two Fishman knots forming a hole. Insert the mouthpiece in the hole and pull from both sides to tighten it down. That is the method that I used on both of my reg sets. I can testify that that method will, under the right circumstances, allow the reg to pull out of the necklace. The other method, which I will probably change to at some point when I'm not being lazy, is to put a zip tie loosely around the mouthpiece. Take a piece of bungee and tie a big knot in each end. Put the bungee through the zip tie (one knotted end on either side of the reg mouthpiece) and tighten the zip tie. That method is about as sure as you can get that the reg won't be able to pull out of the necklace.
Oh, and regarding attaching a bolt snap to your primary 2nd stage: You can do it with cave line. But, an alternative is to use a loop of bicycle inner tube (or equivalent). Make a Prusik Loop through the end of the bolt snap, then do another one around the hose, near the 2nd stage. No knots to come loose. No cave line to get wet and stretch and get loose. Easy to visually inspect the rubber band and tell if it needs to be replaced. In my experience, less likely to move on the hose (but CAN slide, if the bolt snap is clipped to your harness and somebody grabs the reg and pulls it to them - e.g. OOA situation), and the bolt snap is less "floppy". I used cave line for a while but switched to the rubber band setup a few months ago and, so far, I like it better.
