Sorry, I’ve just been “winging” it based upon schematics of other grounded grid Hf amplifiers using similar Russian tubes and 12.6v for filaments. I’m using a cathode choke (150 uh) instead of a ct on the filament transformer. The filament choke I’m using is bi-filar wound. It came out of a dual 3-500z amplifier. It’s overkill for the filament current requirements of these Russian tubes, but I had it and used it.