Team New Zealand have some crunch decisions to make over the next two weeks as the window of opportunity for testing new innovations is about to slam shut.

Since the re-launching their boat in Bermuda three weeks ago, the Kiwi syndicate have continued to chase speed and performance gains on their America's Cup Class catamaran, testing new equipment and finetuning their systems.

With new parts arriving in Bermuda almost daily, the Emirates Team New Zealand shore crew are putting in long hours in the boat shed making upgrades to the high-tech catamaran.

But Team NZ skipper Glenn Ashby says the time for tinkering is coming to an end. Over the next couple of weeks the team's brains trust will be forced to make some crucial decisions on which their America's Cup hopes may hinge.

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"The whole development period over the next two weeks is really critical to getting the boat set-up and getting it reliable for race day," said Ashby.

"So the next week or two is really the last window of opportunity to test equipment and evaluate it and actually give it the green light, or potentially put it on the shelf and not use it. We're very much in the performance development stage at the moment and every day we get out there on the water as a sailing team we're really learning a lot."

The key piece of equipment to be tested over the next two weeks in the lead-up to the start of the America's Cup qualifiers on May 27, is their second set of race daggerboards.

With many components of the America's Cup Class race boats being one-design, the daggerboards - or foils - that lift the boats out of the water are a critical design differentiator between the teams. As the daggerboards have a major impact on the performance of the boats and a significant chunk of the design and engineering effort for this America's Cup has gone into this area.

The Kiwi camp are excited about the potential performance gains that could be garnered from their new set of boards, but they are conscious that several other teams are yet to unveil upgrades of their own.

Ashby said a lot of Team NZ's rivals are still in development mode, making it hard to get a proper read of where each team is at.

"All the teams have been flat out trialing their latest gear and bits and pieces and tuning the boats up, we're doing the same obviously and hopefully we've got quite a bit of performance left in the tank," he said.

"It is quite difficult to gauge how the other teams are going because all the teams are trialing different set-ups all the time. You get a bit of a feeling of who are the strong teams and who are going to be solid down the track, but wit everyone trialing so much different stuff at the moment, you can look absolutely magic one day and terrible the next, so it must be disconcerting for outsiders looking in."

One of the under-performers from the early rounds of practice racing, British team Ben Ainslie Racing, insist they too have plenty of development to come following a "massive" upgrade last week.

In his column for The Telegraph Ainslie came out on the defensive over his team's lacklustre early showings, insisting "reports of our demise have been greatly exaggerated".

"Only this week we launched a new bespoke steering wheel ... which has made a real difference to the way I can control the boat," Ainslie wrote. "And we have other significant performance upgrades coming onto the boat in the next few weeks, which will have a real impact."

The next round of practice racing will be held from May 16-20.