The DFGT is compatible with SP, you just have to work out what each control is called. The attachment is the controls that work with my DFGT, you just have to copy the code from the controller field in the UI. Also, the names of the buttons aren't much help in determining what they do. The only other thing is that you have to have it at 200 degrees lock in the Logitech controller settings to avoid a massive deadzone.
If those controls don't work correctly, then if you open the file in "C:\Program Files\Google\Google SketchUp 8\Plugins\SketchyPhysics3" called ControllerCommands.rb, all the names of the controls are defined, so just try mapping each name to a piston/servo and see what it does.
Hope that helps
The red ones don't seem to be mappable