Aanyone ever replaced propane tanks

I have horizontal non- opd 20`s that I replaced the o ring seals on and had recert. ,they stamped the recert date on the tank , but as soon as I can afford new opd`s Im getting them , if you blow a hose out or get in an accident with the valves open they blow out propane full blast , opd tanks will only blow out fuel at a much lower volume. Probably why they have to have a big sticker on them non -opd, for first responders
In the mean time I`ll be leaving the valves off while traveling and in storage