Propane powered vehicles have been around for years especially for fleets. How often have you heard of one of them blowing up? As long as you don’t break one of the valves on your oxy tanks, they’re safe.
There is quite a difference (x10) in the tank pressure between propane and CNG. To each his own, I have seen enough pictures of ruptured pressure vessels, CNG included, to know I don’t want to be around when Bubba is topping one of.