It would have 100hp power at sea level
Probably, you meant 1000hp.
I have since done a little research. Due to modifications ordered by both the RAF and USN, the weight of those Brewster versions increased, reducing the maneuverability and climb rate considerably.
The Finns were resourceful and made some modifications to the engine that improved oil flow, among other things.
Though they added some pilot armor, their version had tail hooks and life rafts removed etc, so their planes may have never increased in weight like the other versions.
The Finns also decided to make do with what they had, whereas the British simply shuttled the Brewster off to far flung theaters and the US foisted it onto the poor Marines, never really attempting to much address any of the shortcomings.
I have also learned that many of the export versions that ended up in CBI were shipped with second hand transport plane engines.
Other things to consider are that the Brewster was plagued by over heating problems that were exacerbated in hot tropical climates and not as big of an issue in the colder climates the B-239 operated in.
Also one must look at the respective opponents. The Finns never fought the fast, nimble Japanese fighters and I suspect a lot of their kills came against such aircraft as the I-15 and early I-16's.
Midway was the first engagement for the Marine fighter pilots, so yes, they were inexperienced.
Basically we have all the ingredients for a perfect bbs shiitestorm, meaning that everyone is correct to some degree.
I don't know if all the above considerations can account for how well the B-239 performs in AH against the Japanese Zero.
I have held my own against Zeros in the Brewster, and I frankly suck as a pilot.
I find it hard to believe that even the Finnish version would turn so well with the Zeke, but I don't believe it is over modeled to the degree that some here think.
Regardless of the reason, the B-239 will never be accepted as a reasonable sub for either the F2A3 or the B-339, and we basically have an aircraft that fits only in a Continuation War scenario.
Therefore, I would like to see a version with a flight model based on a significantly heavier aircraft at least.