they talking about gain adjustments on the software, it actually adjust the behavior of your machine while it is hovering
by changing your propellers into a bigger ones you might need to adjust your gain, but some people says you dont have too.
It is really depends on your payload/take off weight, and whats the weather status on your flying location
due to the fact that 9443 props will actually give you a bit more flight time, but will make you shots a bit jerky in a windy condition.
check my video last October 03. I took my FC40 in a local park during some heavy and sudden wind gust.
[youtube]https://www.youtube.com/watch?v=k5yaIjNDySw[/youtube]