The stability of the DDG-1000 hull design in heavy seas has been a matter of controversy. In April 2007, naval architect Ken Brower said, "As a ship pitches and heaves at sea, if you have tumblehome instead of a flare, you have no righting energy to make the ship come back up. On the DDG 1000, with the waves coming at you from behind, when a ship pitches down, it can lose transverse stability as the stern comes out of the water – and basically, roll over." The Navy decided not to use a tumblehome hull in the CG(X) cruiser before the program was canceled, which may suggest that there were concerns regarding "Zumwalt"s sea-keeping abilities. However, the tumblehome hull proved seaworthy in a 1/4-scale test of the hull design named "Sea Jet".