Depends on who's flying it. The Charlie (actually, any Hog) only needs one shot to end this fight, whereas the Spit needs either a good long burst or will otherwise need to pick away. The I, V and IX's .303s won't be much more than a nuissance, and while the .50s in the other Marks are more of a concern to the F4U, the Spit can't afford to give the 1C so much as a snapshot.
The 1C can't get too slow. He needs to keep the fight faster where he can put his E retention and high-speed maneuverability advantages to use. If he decides to try and put his flaps into play he better be able to close the deal FAST.