How are people splitting air from scoops into intake, cabin cooling, and
radiator feeds? Are you just partitioning the scoop into separate output
feeds? If so, how large should I make the feed to the intake air for the
engine, and should it have a bypass to allow unused air to escape, or should I
just feed it to the engine compartment/cowl and let the intake pull out what
it will?

I'm planning a single P51-style scoop that drops below the boundary layer, and
I'd like to avoid having separate/extra armpit or similar scoops for other air
supplies.

Thanks,
Chad