I was living OUTCAN when I applied to sponsor my wife, and "moved" her back with me recently while waiting on the application.
The guys at the border were nice and suggested to apply for extension if the application was not completed before the 6 months were up. One of them was even kind enough to check the application on the system and told me there shouldn't be any delays, so I guess that was good news.
I had no idea about the dual intent thingy, so in a way I just winged it. But I did it partly because when we came to look for houses before I moved back, the guy at the border at that time asked me if I had already applied for her PR, and said that some people wait until they move back which is a mistake because it delays things.