I have a couple of 100 steels that need to be christened if you don’t have a tank I think they have 33% Nitrox, I have an analyzer so that shouldn’t be a problem I also have AOW Nitrox, but have not worried about the wrecks or any other certs. weighting is not much in the springs... alot more in the salt.. I use about 8 pounds in the fresh and 28 in the salt with my 80 cu aluminum but have to weight myself to the steels yet if you need to weight yourself in salt then the Blue heron bridge is a good shore dive