FSX Ground polygon layers order

hi everyone
I am making a GP but I have a terrain issue.
I made a GP and converted it with MCX using ground polygon wizard and set the altitude to 250 meters
then I used ADE to modify and edit some taxiways of my airport and set the airport altitude to 249.50 meters, then made a flat terrain polygon also using ADE and set it to thesame altitude of the airport but I have parts of the terrain showing trough the GP even when the GP altitude is higher than the flat poly and airport altitude so my question is: what goes first or which is the correct order to place the layers
The altitude set in the GP Wizard, the airport altitude, and the flat terrain polygon should all be the exact same value. You are seeing the terrain showing through because the GP Wizard is different. FSX will place the ground polygon on top of landclass textures, aprons, and runways. The ground polygon is drawn last by FSX. Layers in the ground polygon allow you to create tire marks or cracks for instance on top of a concrete texture that makes up your runway.