Wrong. The main.swf is not edited. It's simply proxied through SH-IT and has an attribute added on top of it so SH-IT knows to run it. All the attribute does is says "SH-IT, RUN ME! Everyone else, give them to the default SWF player". The reason I do this is my SWF player source isn't the best so I have no idea how it would do running other SWF files. This attribute simply allows me to pass on the SWFs to the default runtime. What SH-IT does is hooks Peperflash and the default COM object for Flash and whilst its running, it simply replaces the installed flash player with mine. My Flash player then loads the main.swf and plays it as if peperflash inside chromium was playing it. However my peperflash is edited so it intercepts certain bytecode calls and injects code, hence how most of this stuff works.
I can't add loads of code as it is WAY to complex and just getting this working took me for ages. As soon as you edit main.swf, Bigpoints hash checking algo finds it and then refuses to load the swf. Thats why I had to resort to writing my own PeperFlash plugin.
As for custom designs, thats easy peasy and doesn't even need SH-IT. Simply proxy the request for the ship designs SWF and replace it with your own. Even better, modify resources.xml and add your own :P
-jD