A hydrogen filling station accounts for variabilities between tank systems when filling compressed gas tanks. To identify a theta value that accurately reflects the conditions and performance of a particular tank system, one or more test parameters are determined, and one or more margins associated with one or more test fills of a fuel tank are identified, where each test fill corresponds to a respective test parameter. A proposed theta value for controlling one or more fuel deliveries to the fuel tank is determined based on the test parameters and the margins. In this manner, the theta value enables hydrogen refueling of a compressed gas tank to be improved.