RE: CARF F4U-1 Corsair build thread
Here is a look from the inside. The blue line is the tape on the outside. This small gap gives the flaps the room they need to operate. Not much is required because they 'retract' into the groove you made in the ply rings, when they open.
The space between the blue line and the bracket is where the front ring will rest.
You can also see how the blind nut in the cowl mount protrudes through the plywood. This aids in alignment of the bolts when installing the cowl. It is firmly in it's place when you install the bolts from the back, through the cowl flaps.