My Corsair book says the control surfaces (at least the ailerons) went metal sheeted with the F4U-4 and the outer wings metalized with the F4U-5. However, it is correct that most flying F4U's have all metal surfaces, but this is a matter of maintenance practicality as the fabric would require recovering and replacement, something most owners would rather not worry about.
All F4U series had Ailerons that were Wood structure with Plywood sheathing covered with Fabric.
If owners are concerned with originality they will use fabric. Today's modern fabrics can last many years. A FG-1D I worked on in the mid 1990s had fabric applied in the early 1970s on it.
There are some F4U's that still have the fabric covering on the wings. The fabric went from the wing spar to the trailing edge. Access panels, gun bay panels were alum as well as the exterior of the ammo cans on the top surface also was the exterior skin surface. The wing leading edge was alum skin. Earliest models had leading edge fuel tanks.
The rudder and Elevators were fabric covered on all the F4U versions I'm aware of. Maybe AU-1 might be different.