Question Mares MR22T with Abyss 2nd stage, 1/2" port, and routing options

[ManImCool]

I recently acquired a Mares MR22T 1st stage with Abyss 2nd stage (specifically bought the sets in this thread) and after diving them for a week, absolutely love them.

However, despite shifting the tank bands/tank as much as possible, I constantly find myself hitting the back of my head on the 1st stage when lifting my head. It looks like if I were to simply turn the 1st stage upside down, I'd no longer have any issues with hitting my head on it. I use a BP/W setup.

I thought turning the 1st stage upside down would be a simple affair until I realized that the primary 2nd stage is hooked up to a 1/2" port on the first stage, not the standard 3/8" port. The 3 remaining low pressure ports are 3/8". There is no 1/2" port on the other side of the 1st stage that I can use if I were to flip it upside down.

Which leads me to some questions:
Does my first stage or primary Abyss 2nd stage require the use of the larger 1/2" port? If so, why?

If not, can I simply use some sort of 1/2" 3/8" adapter from DGX (whether located at the 1st stage connection or the 2nd stage/mouthpiece connection), or would that not work? Any other options?

If I can use the Abyss 2nd stage on a 3/8" port, are there any downsides to using the smaller size, whether merely a mild annoyance to a serious life-threatening danger?

Finally - if I'm stuck with the 2nd stage being forever mated with the 1/2" on that one side, are there any realistic hose routing options if I were to turn the 1st stage upside down anyway and have my 2nd stages sticking out from my left? I'm currently using the traditional 2nd stage/octo hose length setup taught in PADI, but am open to changing to primary donate configuration if it gives me better options.

Thanks!

 

[Zef]

The 1/2-inch LP port on the Abyss 2nd stage is the DFC port (dynamic flow control) intended to be used with the diver's primary 2nd stage regulator. The DFC port is supposed to be a more direct channel of air from the tank, through the first stage, out to the 2nd stage, and supposed to deliver increase/better flow. In reality/real life diving, there is little difference in the flow rate between the 4 LP ports around the MR22 body.

When the majority of the industry standardized on the 3/8th LP fitting, it caused LP hoses with 1/2 inch fittings "less available" in the broader market. While they are available, many shops don't stock them. The response to this, is to either special order a hose, or place 1/2-inch male adapter to 3/8th female adapter in place between a now standard 3/8th fitting hose and the 1st stage. Using an adapter makes it much easier to find a replacement hose, if needed, when travling to dive.

Bottom line is that you can safely use any of the LP ports on your MR22 to route your primary 2nd stage, so you can either move your hose with the 1/2-inch fitting to your octo and use that on the DFC port, or you can purchase an adapter to reduce the fitting size from 1/2 to 3/8th inch to get your primary on the 1/2-inch hose to work on one of the alternate ports.

Another option, if your 1st stage is a yoke/international type, then I recommend switching it to DIN. The DIN fitting should move your MR22 slightly further from the back of your head, which may be enough to keep you from hitting it.

-Z