Ok, I've installed the scenery files and loaded EFJO into the most recent ADE. . .all the custom objects show as black squares (unknown). Here's what I did; went to "Tools"/"Library Object Manager". From there clicked on "Add Folder" and browsed to the "scenery" folder for the Finnish Airports scenery. From there it will search each bgl looking for objects, you'll have to click through each one but when you're done it will have loaded all objects (unknown) into it's system. You can reload the Airport and it will now show all custom objects available. From there, I would think adding parking spaces will work fine. When you loaded the airport into ADE and added your parking spaces, then saved and compiled it was eliminating all the custom objects because it couldn't find them.