This is the first time I've done scenery Using Airport for Windows 2.6 using FS2002. My previous projects were all in FS98! The test airport I'm working on has an elevation of 501.4 feet. I used a polygon to create an apron area and when I tested the scenery I noticed lumps of Fs Grass on the apron. I deleted the scenery from the scenery library then went back into Airport and added a Flatten area around the Apron polygon set for 501 feet exactly. I was worried about going too low and effecting aircraft taxiing across the apron. I saved the edits and compiled the scenery with no errors! Then I started up FS2002 and reinstalled the scenery into the library using a new name. Now when I tested the changes I still have lumps! Did I miss something in creating the flatten area, or can I just go lower with the height?