Extruded Periodic Pair warning help

siw

Hi,

I'm meshing an aerofoil for a 2-D simulation. I've set up an Extruded Perodic Pair in the spanwise direction to that I get 1 element thickness. However, when applying the various spacings, controls etc and viewing the surface mesh I always get the following warning:

One of more face or edge spacings may not have the desired effect because they have been set to objects that are not associated with the extruded periodic pair. You might want to try using point, line or triangle controls to achieve the required mesh spacing in the periodic regions.

What does this really mean and how do I fix it?

I've got point controls on the leading and trailing edges, on both sides of the periodic walls to increase the meash density at these curved places.

Thanks