This is what I do. First, I go to my SF2:I mod folder (IE: the main modd folder, not Objects or something, the base SF2:I mod folder.) and rename it to xStrikeFighters2 Israel. Then run the stock SF2:I, and that will create a new unmodded SF2:I folder. Then install ALL your DLCs. After their done installing, find the DLC aircraft you installed and drag them out of the Aircraft folder to your desktop or something. Then, delete the unmodded SF2:I folder that the game created when you ran it. Rename your modded install back to StrikeFighters2 Israel. Then all you have to do is drag and drop your DLC aircraft from your desktop to your modded "Aircraft" folder, and Wallah! Hope that helps!
liamp51