I'm sorry if this has been covered before, but I am looking for a definitive answer. I just inherited 2 LP Faber 130s that has the 2400+ symbol on them and the guy told me you could pump these tanks up to 4000psi in "cave" country. Then I ran across a thread that said LP tanks are made with a different material than HP tanks. So are we wrong about pumping the tanks up past their rated pressure that we have heard and done for many years?