MacArthur was a guest of Team New Zealand

The Kiwis beat the German entry, as BMW Oracle and Italy's Luna Rossa clinched the first semi-final spots in Spain.

"I tried to watch everyone individually to see what they did to try to get a better understanding," said MacArthur.

"It was fascinating and it worked very well. It was fantastic racing and it was great to be on board a happy boat."

Victory over United Internet Team Germany in flight seven means Team New Zealand are the only syndicate in the 11-boat fleet to be unbeaten in round robin two off Valencia.

MacArthur added: "I was really impressed with the atmosphere between the guys and going out there and it was nice to go right out on the boat and come all the way back in, because you see the whole cycle.

"So I really, really enjoyed it, it was great."

BMW Oracle and Luna Rossa are tied on 31 points, one point clear of the Kiwis, with the top four teams going through to the semi from 14 to 24 May.

"We are very happy to be through to the semi-finals," said BMW Oracle navigator Peter Isler. "It is only one step on a long journey and we know there is still a lot of work to do."

Spain's Desafio beat Mascalzone of Italy in a rematch of flight four, which moved them five points clear of Sweden's Victory Challenge in fourth place.

The Italians had won Wednesday's encounter but were penalised for an infringement in using their backstay during the race against America's Cup Class rules.

BMW Oracle earlier scored an emphatic victory by one minute, 28 seconds at the final mark over Areva Challenge of France, who saw their lingering chance of progress evaporate.

Luna Rossa, sharing the top of the leaderboard with BMW Oracle at the start of the day, took early control over compatriots +39 Challenge, who were hit with a penalty as their rivals ultimately cruised to a 1:04 win.

The winners of the Louis Vuitton Cup challenger series will face holders Alinghi for the America's Cup from 23 June-7 July.