Team NZ and BMW Oracle have faith in the measurers to put pressure on anyone looking to get away with an illegal swinging keel.

One of the America's Cup teams have asked the measurer questions in relation to reducing the deflection of the keel.

Devices that move the keel are not permitted, but it is understood a number of teams have been looking at a way of linking the fin to the rig so that when the boat heels over, the pressure comes on the fin via the rig, which may reduce the deflection on the keel. That could be legal.

Emirates Team New Zealand managing director Grant Dalton said they were aware of it and had looked at the rules.

"Maybe there is a way that it can be done - it is not obvious to us, but I know the measurer Ken [McAlpine] will be looking at that pretty hard and we have faith in his ability to spot anyone that is trying one on," Dalton said.

"Our reading of the rule is that it is quite clear it is illegal. The rule is quite specific about trying to move ballast and using a device to produce a mechanism of moving ballast other than the ability of the water".

"We have got absolute faith in the measurers to police and question anybody that is obviously trying to do it."

Those sentiments were echoed by Chris Dickson's BMW Oracle Racing.

"This type of keel is illegal under the rules and we have not developed such a keel" said the Team in a short statement. "We have every confidence in the measurers ensuring all competitors will use only legal equipment. We are sure the measurers are already on top of this situation."

Defenders Alinghi, thought to be one of the teams trialling the concept, would not comment but designer Rolf Vrolijk told the German press: "We are happy if dock talk continues in this direction. This will be a distraction for all."

Dalton acknowledged it could be a bluff.

"I know all of that is supposedly part of the America's Cup game but I think this team is a little more resilient to double bluffs and all those things to not throw it off its stride."