Go to hangar, select the plane you want to skin, go up to the skin select, right click and choose 'Save Default Skin'. Then a folder will appear in C:\Program Files\HTC\Aces High II\Skins, and in that folder will be the bitmaps for the aircraft's skin. Rename the folder as the next skin (if theres, say, 8 F6F skins, your folder should be F6F5_9). Then put in a file called F6F5 or whatever the plane is and put **** by **** and the skin can be selected in the hangar offline.