If my information was incorrect then this was your chance to enlighten the misinformed. I have no doubt in my mind that you're more knowledgable about diving than I am. I still don't agree with using the manifold in a cave. In open water I can see the benefits but not in an overhead environment. I can easily hand off one of my cylinders to someone in an emergency and they can rig it like a stage bottle, whether back mount or sidemount. This can't be done with the manifold. I can also remove my tanks if needed with no issues where the manifold has a quick disconnect that will allow small amounts of water to get into the system before the second stage if taken apart underwater. It's an unneeded luxury that is nice to have but would not make me feel safe in an overhead environment. The chances are that you won't be able to convince me the UTD manifold is good to use in overhead but I'm still open minded and would at least like to hear what you have to say so that I"m at least properly informed.
I’ll try to offer any knowledge I have of the system, it’s great that your legitimately interested with an open mind, there have been Z system discussions ad nausem on SB and it can make anyone gun shy trying to offer knowledge when most have made up their mind already. So, to address some points....
The cylinders can be handed off quite easily, further, with the quick connects and manifold it’s very straight forward and also allows both divers to remain on the long hose. Yes, a very small and unnoticeable amount of water may get to the second stage (maybe 1 or 2 ml) and manifold. A simple post dive rinse takes care of this. My preference is not to hand off cylinders unless no other options available. Certainly handing off cylinders in a confined overhead in zero Vis is a challenge.
Simply, the manifold allows a diver to always donate from the long hose instantly, following the muscle memory learned since open water dive one. When it comes to overheads, yes, more failure points (more static O rings and 2 QC6 connections) but the manifold is protected far better than a backmount manifold as it’s tucked behind the divers neck. If there is a second stage failure, the system gives access to all the gas unlike traditional SM where the cylinder with the failure now has unusable gas and impacts your gas plan.
Drawbacks are cost, complexity, the requirement to dive in a team and training.
If you do have questions feel free to ask, cheers.
