3. If you tend to overbreathe the reg when you are working hard, there is another reg available, the SRG-1 Stealth regulator, compatible with the Guardian, that is designed to deliver a greater volumn of air to help solve this problem.
(If anyone is considering buying a ffm for the first time I would recommend that one of your tests should be to work the mask so that you get huffing and puffing enough to try and overbreathe it. Apparently this feature is very important for you search and rescue types who are under great physical exertion while rescuing or retrieving a body.)