From the DSV information in the website store.
Argonaut DSV.....Dive-Surface-Valve was developed to address the following.
Double hose regulator freeflow at the surface when the regulator body is lower than the mouthpiece. By closing off the mouthpiece opening during surface swims, during training or while performing surface swims the need to put the hose loop under your arm or using an separate plug in the mouthpiece outlet to prevent freeflow is eliminated.
Allows the user to select mouthpieces currently available for single hose regulators which addresses complaints of jaw and tooth pain when using the standard curved mouthpiece.
Newly designed airflow diverter increases venturi and directs airflow towards the diver for easier breathing. Diverter enhances venturi airflow to the diver and virtually eliminates air being bypassed down the exhaust hose during inhalation. While testing the new DSV on the Argonaut Kraken most divers found it impossible to overbreathe the regulator.
From the first post in the 15 page thread about the DSV.
2. You will be able to use the mouthpiece of your choice. You have dozens of options available from the single hose regulator market. I will stock several varieties in the store so you can buy one with your DSV or get it without one and use a mouthpiece you may already like using.
Doing it right should include some common sense, not just blindly following specs and instructions. .Gary D, AWAP on SB