Despite piecemeal deployment, an impossible tactical situation and novice fighter pilots, the N1K1-J performed rather well against Allied fighters and it was one of the few Axis types capable of posing a serious hazard to a P-51D or a Vought Corsair.
"a serious hazard to a P-51D or a Vought Corsair" と書いてあるから、P-51Dに見劣りしないってことかな。
Specification of Brewster F2A-1: Powerplant: One Wright R-1820-34 Cyclone nine-cylinder single-row air-cooled radial engine, rated at 940 hp. Performance: Maximum speed of 311 mph at 18,000 feet, and a maximum speed of 271 mph at sea level. Initial climb rate 3060 ft/min. Service ceiling 32,500 feet. Maximum range 1545 miles. Weights: 3785 pounds empty, 5055 pounds gross, 5370 pounds maximum takeoff. Dimensions: Wingspan 35 feet 0 inches, length 26 feet 0 inches, height 11 feet 8 inches, wing area 209 square feet. Armament: Three 0.50 inch machine guns, one 0.30-inch machine gun.
Specification of Brewster Buffalo Mk. I (Model B 339E): Powerplant: One Wright R-1820-G105A Cyclone nine-cylinder, single-row air-cooled radial, rated at 1100 hp for takeoff. Performance: Maximum speed of 324 mph at 21,000 feet, 313 mph at 13,000 feet. Cruising speed 256 mph. Initial climb rate 2600 ft/min. An altitude of 15,000 feet could be reached in 6.3 minutes. Service ceiling 30,675 feet. Weights: 4479 pounds empty, 6500 pounds gross, 6840 pounds maximum takeoff. Dimensions: Wingspan 35 feet 0 inches, length 26 feet 0 inches, height 12 feet 1 inches, wing area 209 square feet. Armament: Two 0.50 inch machine guns in the wings, two 0.30-inch machine guns in the upper fuselage.
The F2A-1s diverted to Finland were given the company designation B-239. The naval equipment (tail hook, life raft, catapult harness) was removed, and the telescopic sight was replaced by a simple bead and sight arrangement. Armament consisted of one 0.30-in and one 0.50-in machine gun in the cowling, plus two 0.50-in machine guns in the wings. The engine was replaced by an export-approved 950 hp Wright R-1820-G5 radial. Maximum speed was 297 mph at 15,580 feet and service ceiling was 32,500 feet. Empty weight was 3900 pounds, and maximum weight was 5820 pounds. http://home.att.net/~jbaugher1/f2a_3.html
AIR FORCE LEGENDS SERIES P-51H MUSTANG の記事に拠ると、P-51Hは高高度性能は P-51Dより優っていたが低高度では大差なかったと書かれています。 P-51Hは朝鮮戦争当事現役だったのに関わらず、何故実戦参加しなかったのか その理由は載っていませんが、P-51Hの降着装置はP-51D軽量化されていた為に 前線での運用に向かなかったのかも知れません。P-51DとP-51Hの性能が低高度で 違わなければ、近接支援に旧型のP-51Dが適していたのかも知れません。