For a 2-position setup, you should use the case where you need the flaps the most, all the way down for landing, or retracted.
The takeoff condition doesn't normally need flaps.
I've tried a variable channel with all positions dialable via a knob, but that's much clumsier to use than switching.
A P-51 of course MUST have flaps down to land!
Anything else just doesn't look right!