Installing a new airport in FS9

Help,
I'm at the end of my thether !
I have created an airport ( Martlesham Heath in Suffolk, pre war test centre for Spitfire amongst many others) I tried using AFCAD, but could not get rid of the autogen scenery ( FS9 trees and buildings ) within the airfield and on the runway. I then tried an exclude and flatten area using FSSC, but this just got rid of the AFCAD airfield and left the autogen intact.
I then tried adding an exclude area to my FS9 Scenery config file. This got rid of the autogen stuff , but also every other scenery item from FSSC or AFCAD.
What am I doing wrong??? I know I could set autogen to minimum , but this is not a real answer.
I'm at the end of my thether !
I have created an airport ( Martlesham Heath in Suffolk, pre war test centre for Spitfire amongst many others) I tried using AFCAD, but could not get rid of the autogen scenery ( FS9 trees and buildings ) within the airfield and on the runway. I then tried an exclude and flatten area using FSSC, but this just got rid of the AFCAD airfield and left the autogen intact.
I then tried adding an exclude area to my FS9 Scenery config file. This got rid of the autogen stuff , but also every other scenery item from FSSC or AFCAD.
What am I doing wrong??? I know I could set autogen to minimum , but this is not a real answer.