Downwind, only the skipper can see the layline, the crew can't see anything behind the kite! (at least on my boat) Upwind they can both see it. I did not mean to imply that the crew should stare at the sails the entire time, but in his video, unless his head cam was pointed down while his eyes were up, he -never- looked at the sails. An over trimmmed kite is slow.

Go watch the Mischa upwind video on the CRAW site (thanks for that TEH!) Even he looks at the sails once in a while. I think he said he spends his time looking outside the boat vs. inside, about 70/30, but zero "inside" is not a fast option, especially when it comes to the spinnaker.

Oh, and if you crew for me, bring your blender... ;^)