это не мои слова....а Джима Ванька, президента Спорткоптера, по поводу крестообразного оперения ( см сайт: http://www.sportcopter.com/Gyroplanes/SportcopterII/tabid/133/Default.aspx)
WHY WE CHANGED THE TAIL DESIGN
This decision was made after a year of testing with several configurations. Also the cruciform tail seemed to "hunt" at high speeds and this needed to be changed. We are very pleased with the new tail design as it far outperformed the cruciform design and has fixed the stability issues for both pitch and yaw. The horizontal stabilizer has a slightly larger surface than before, and because it is out in cleaner airflow it is not starved during quickly reduced power settings.