ImgBurn doesn't do the compression that is done in Fab,
after opening Fab select main movie, then remove any titles you don't want.
then go into common setting BD 2 BD ..> in the default size drop down choose the BD 9 you want.
Then go back to the Fab window and in the Quality box set the appropriate size let it scan when that is finished, let it rip expect this to take a while 3-4 hours is not unusual.
depending of course on your systems components