Running LP at high altitude is more a problem of getting the liquid in the tanks to flash-up to a gas. The regulator will do it's best to compensate, but if there is little pressure in the tank it won't work. Readjust the pressure is a bad idea for when you return to lower levels. Short-term heating the tank would work, long-term (stationary appliances) changing the orifices is what we do. You probably wouldn't like the way I heat the tanks; I use a torch (yes and open flame on the tank) and no I haven't blown up yet (I've been doing this job for 54 years). I guess you need to know how and where to put the flame.
Yup, 12" WC is pretty close to a half pound, but that's a real pour way of measuring it.
