Aaagogo,
Get your Cave diver Lawer buddy to look into the CFRs and tell you what it says about having overpressurized cylinders. Hate to tell you but what people do, what they get away with, and what is legal or not are seperate issues.
Sure if you fill your own tanks, stay on the land you own that has the fillstation & Dive site, and dive your private site you could skirt the criminal penalties. but if you had someone on property with you that was affected you have set yourself up for Civil court.
Your mentallity states that I could load up my pick-up full of TNT drive down the street to the marina load it into my buddy's boat and toole around the port picking up chicks at the bar and nobody could do squat about it because "it was my stuff".
Once you affect others, your actions are no longer private and that is why we have governing agencies over all aspects of our lives, because we don't always use the best judgment.