The 500 psi is a great idea I say that because as i was doing my check out dive we were in about 45 ft of water and as the tank went from 3000 to 1500 +/- I shot up and out of the water like a torpedo was not a good thing thank god it was only 40 + feet so if anything take on a few more lb then you think to be safe .I also found that I can only use steal tanks do to the rapid change of aluminum tanks .