OTL "Butterfly flaps" slide back before tilting down. They increase wing area (a bit) before tilting down to increase drag. Those Japanese fighters were among the few to use "butterfly flaps" to assist maneuvering.
OTOH An updated version: double-slotted Fowler flaps are widely used on modern airliners. Because they tilt down, they are severely restricted to only extend at lower airspeeds. Deploying Fowler flaps at too high and airspeed will bend them or rip them off the airplane!
I doubt if "butterfly flaps" would lower P-51D stall speed significantly below the 90 knot limit on USN arrester cables. That would require full-span flaps, which would drive a radical redesign of ailerons.
P-51H was never seriously considered for carrier conversion because it was lighter and less strong than earlier models of P-51.
OTOH An updated version: double-slotted Fowler flaps are widely used on modern airliners. Because they tilt down, they are severely restricted to only extend at lower airspeeds. Deploying Fowler flaps at too high and airspeed will bend them or rip them off the airplane!
I doubt if "butterfly flaps" would lower P-51D stall speed significantly below the 90 knot limit on USN arrester cables. That would require full-span flaps, which would drive a radical redesign of ailerons.
P-51H was never seriously considered for carrier conversion because it was lighter and less strong than earlier models of P-51.