I don't worry about the G-bar, I just figure dev. by using the SBR and recommendations from others that have done the testing. Such as Sandy Kings testing of pyrocat-hd for films I use or the dev. times for using D-76 from the Dick Arentz book. They may not be exact but they are very close. Both give recommended times for different SBR's to obtain a neg. for printing with palladium which is all I use. Hope this helps.