We heated our bottles like that for years in Top Sportsman and those were IHRA divivional events. They tech the shit out of you at those races and we never had any problems heating our bottles with torches, everyone did it that way, but yjres have changed a lot since then. Its actually not that dangerous if you do it right. The bottles have a pop off valve on them anyways. We never went abouve 1200 PSI though. I think they are 900 PSI with just a room temp full bottle.