first of all, you need a hud crosshair that is a regular cross,
secondly, cl_crosshair_file crosshair6
cl_crosshair_scale 40 (45, 50, experiment with it)

The one at the time that you mentioned seems to be a fog cross In combination with a built in game crosshair. I use something similar to this, with a combination of a built in game crosshair and one of the knuckles crosses. I'll post a screenshot when I get the chance

Edit: here is my crosshair:
first picture (on top) is with crosshair 1 and built in crosshair 5
second picture (on bottom) is with crosshair 0

I think I can try and recreate what you saw in the video, if you're interested. I'll put the settings for it when I've got it