Cropping start time for filmstrips

When comparing 2 WPT charts, is there a way to indicate the start time and crop the initial white frames? In most of my use case, I want to show how one version of site is slower than the other and the initial white frames that appear in both WPT results is not of much interest.

I know that there is a query parameter to indicate the stop time for the filmstrip but, could not find anything to indicate the start time.

+1 for this.

I think when you are doing frontend analysis on different runs an option to normalise or remove backend time, and therefore get rid of backend response variations would be a great thing. So the far leftmost would be the arrival of the HTML. After that, that’s what we can affect with frontend work.