Rob Waddell is backing a "first past the post" format when it comes to the battle for who will be New Zealand's single sculler at the Olympic Games.

Waddell has now won two out of two head-to-head races with Mahe Drysdale with a half length victory in yesterday's Cambridge Town Cup on Lake Karapiro.

The trial format is still a work in progress although it has been established there will be three trial races including the national championship final. Waddell wants a "fastest sculler wins" format to give him an incentive.

The two of them will duel again this weekend at the North Island championships.