What's the trick to getting the skin thumbnail to show up in the hangar menu?
The easy way is to download my latest skins and you will see where and how they go.
To make your own:
Take a screenshot of the plane you want to add and edit crop resize the picture to 300 X 100 pixels jpg.
Useing Dr1 as an example.
Make these folders if you don't have them. C:\Program Files\Rise of Flight\data\swf\planes\fokker dr.i\skins.
The SWR folder you have so make the others. Drop your picture in the skins folder and make sure you name it exactly the same as the plane you took a picture of from the planes name as it is labled on the dds file.
Repeat for any other plane. Example for SE5: C:\Program Files\Rise of Flight\data\swf\planes\s.e.5a\skins