Be careful. The Corsair in the thread listed above is an F4U-5N which is a post war variant of the Corsair and does indeed have the 20mm guns protruding from the wings. Only the cannon armed Corsairs had that protrusion of the gun barrels.
If the model you are building is a six gun, 50 Caliber model from the WWII era, then the guns do not protrude. There is a smooth "channel" around the barrels that curves around from the leading edge of the wing, but the barrels do not stick out.
Here's a link to Vintage Wings of Canada's FG-1D showing the three gun ports on on wing. You can see the barrels, but they stay within the wing.
http://www.williammaloney.com/Aviation/ ... ngGuns.htmI believe the F4U-1C was the only 20mm cannon armed version mass produced during the war (about 200 built if I recall) and they had the cannon barrels protruding.
I hope this helps.
Jerry