How to customize webpagetest?

[Timook]

WPT is a very useful tool, but now I have a customized need, just want to let WPT help me to record the screen, and identify the first screen to load the completion time (because this is more accurate response to the user to load the first screen Time feeling), the other does not need (such as Waterfall and so on, because it will make the first screen load time longer a little bit, and the user real feelings of the first screen time is not the same), thank you.