The old R22 window AC that I filled with R134a is still running great, but it's time to try something new. So I bought R290 refrigerant (propane) to fill the system with. Yes, I know that it's flammable, so please don't go there. My question is what pressure do I fill it to? Or would I be better off just charging it in very small amounts with a thermometer in the vent and once the temp starts to go up, take a little out so it's the coldest? Thanks.