That penalty on JPN was pretty hard to tell - glad I'm not a judge...
Closing speeds were enormous. Center of rotation on these boats is somewhere around the foil, but there is side slip and other factors to consider.
Is causing a nose-dive because of a super-sharp turn to avoid another boat considered "seamanlike fashion"? Can I close the door at A-mark such that a port-tacker has to "crash tack" to avoid me?
I mean, I can see NZL making some of their tacks in what appears to be 1/2 boatlength, but this was a 270 degree turn around an obstruction.
Given the fact, too, that you can't throw the helm over without a foil being down, among other things in the turning sequence...
So does the umpire have to consider "seaman like fashion" the whole process (foil down, wing trim, crew movement) when determining the room to tack? Or a set distance (say 1 boatlength) from the mark?
If it's the process, then I can see it takes several boatlengths to change tack if you start from foil lowering to opposite foil retraction.
If it's just "start-of-turn" type judgement then I think Nathan went a little long before throwing the helm (to draw the foul)
Now Barker didn't have the benefit of that big yellow circle around the mark, and may have actually thought he'd sail up an over Outerage... while keeping the door closed as much as feasible.
At 30 kts closing speed, it may be difficult to judge just how much room someone needs... Especially when that big giant spear-like carbon sprit is pointing RIGHT AT YOU going 20 kts