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Strafing aircraft must approach within small arms range. Most important requirement is protection of pilot against rifle/LMG rounds.
Smaller is better. Larger aircraft such as Ju-88 and B-25 can strafe just fine but they make large and expensive targets.
You might surprise the enemy once but if you come back for a second strafing run every soldier on the ground will be firing at cyclic rate. So you want enough firepower to get the job done with a single pass.
And the winner is....
Fw-190F. Well protected, heavily armed, small and fast. Wing hardpoints should contain cluster bombs, rockets or additional cannon for this dangerous mission.
Were P-47 pilots protected against 7.92mm AP rounds coming from below?P-47 for obvious reasons- could absorb a lot of punishment deliver the goods.
Hanging 30mm and above guns on a plane and it has gone from "strafer" to anti-tank.