Note how nicely Jamie and Ben (4594) have everything pulling as they move past the still struggling WindShadow team, and yet Frank and Kim continue to pull away. The spinnaker is likely not helping the Abbotts here. It's a tough call whether or not to douse the chute in this situation.
Assuming that Frank is headed straight for the leeward mark (likely!), it's a gamble for Jamie (4594) to dive down right now, and yet it might be a gamble worth taking. Keeping to their current course will leave Jamie and Ben frustrated the whole leg long - knowing that no matter how well they move, they'll never get past Frank.
On the other hand, if they dive down four boatlengths here and get through Frank's wind shadow, they can make a foot race out of it and possibly get past Frank by taking advantage of their spinnaker. The wind has been shifty and could well come back closer to its previous direction, making the reach appreciably broader, and making it advantageous to be off to leeward. Even a further header wouldn't be bad here for a leeward boat: the spi would come down and then the leeward/ahead boat might be able to "gas" the windward/astern boat while sailing close-hauled.
Of course, Andrew (4610) might grumble since it would, at first glance, appear that Jamie breaks Rule 17.2 by diving down in front of Andrew so close to him, but that Rule in fact prevents the windward boat only from sailing  "below her proper course" which is any course Jamie might reasonably sail here, if Andrew's boat were not there at all. And as was just pointed out, trying to go through to leeward of Frank would be a reasonable course of action to take. Of course, Jamie would still have to keep clear of Andrew if Rule 11 (windward/leeward) were to enter into the picture.

Near the leeward mark, with National Capital Regatta action in the background: Looks like the reach did end up being too close for advantageous spinnaker work. Hard to imagine how Dave (282) could have lost 2nd place on a reach like this, unless he held his chute too long, which would also explain why he is off to leeward. This sequence of pictures is misleading, making it appear as though Dave may get buried by windward boats. If he is in any doubt about reaching the mark clear ahead of the two inside boats, he should now defend the "inside" (and his wind) - generally a wise strategy on the second reach.

... Andrew (4610). Jamie (4594), meanwhile, could benefit from the Stuart Walker advice to "slow down and win!" Rounding with his bow to leeward of 4610 traps Jamie, a bad situation to be in at any time, but especially here where John (7351) is so close behind. John, of course, won't be rounding the mark at full speed, having sheeted his main to closehauled far too soon - something that is more damaging than undersheeting (luffing) a similar amount. (I know, I know! It's easy for me to sit at my computer, under no pressure, and criticize. But please be assured that it's the teacher in me talking, and I just can't resist using the critique as a teaching moment, as they say.)

Now it would be perfect, if at this moment a picture of me popped up where I could point out an error of my ways, but alas, it was not to be: Al and Marc have put part of their considerable lead over John (who is the one boat they really can't afford, series-wise, to lose to) onto each tack, such that by tacking here as John rounds, they are on the same tack as John and placed directly between John and the next mark. And what can I say: the jib is perfect (slightly undersheeted for first gear, coming out of the tack), as is the main which Al has in his right hand (take my word for it!) and ready to ease if necessary. Even Al's bathing suit is not hanging halfway down his rectal derrière this time! Of course, Al's PFD is undone, but this too is intentional, a mute protest against the club rule that always requires PFD's to be worn, even on hot, light-air days such as this one!!

Here, Dave and Carol (282) have a lovely puff and lift that is letting them outpoint Uncle Al (centre) by at least 20°. Textbook wisdom calls for Al to tack, when he sees the boat to windward and astern sailing much higher and discovers that he is thus sailing the knocked tack. But Al's #1 priority remains not to let John beat him in both of the first two series races, so he will, above all, sail to stay directly between John and the windward mark.