When a B9 part switch is integrated with an RF tank, it does not remember any resources the player adds to the tank.
The default resources assigned to the tank will function as expected, either scaling with volume or switching to whatever the variant defaults are set to. However, if the player edits the resources in the tank, it will not save and will simply revert to the whatever the default fuel load for the variant is the next time the craft file is loaded. The tank must be edited immediately before the craft is launched to remember it's contents.
What the intended behavior should be is not really defined. In my opinion, wiping the tank contents to default when the variant is switched is probably going to be required to avoid accidently overfilling the tank and/or allowing an invalid propellant.
The ROEngines Agena Equipment Rack is a good example of this. To reproduce, just assemble a craft that contains the Agena Equipment Rack, edit the propellant load of the equipment rack, then leave and re-enter the VAB and load the same craft again.
When a B9 part switch is integrated with an RF tank, it does not remember any resources the player adds to the tank.
The default resources assigned to the tank will function as expected, either scaling with volume or switching to whatever the variant defaults are set to. However, if the player edits the resources in the tank, it will not save and will simply revert to the whatever the default fuel load for the variant is the next time the craft file is loaded. The tank must be edited immediately before the craft is launched to remember it's contents.
What the intended behavior should be is not really defined. In my opinion, wiping the tank contents to default when the variant is switched is probably going to be required to avoid accidently overfilling the tank and/or allowing an invalid propellant.
The ROEngines Agena Equipment Rack is a good example of this. To reproduce, just assemble a craft that contains the Agena Equipment Rack, edit the propellant load of the equipment rack, then leave and re-enter the VAB and load the same craft again.