Extended plates keep the nose down (obviously). Plates like Rivas "groovy" plate and JetDynamics concave plates offer a slight advatage to handeling. The D cut plate is primairly for surf ridding. It is to keep the nose up, not down, when on the face of a wave. I was running a stocker with the D cut, which worked ok on the surf, but sucked for handeling and at more than 3/4 throtle the ski was really loose.
My JetDynamics plate worked good for handeling, but not so good in the surf. So.... I D cut the Jet Dynamics plate and now have the best of both worlds. I don't recomend the D cut if you are a flat water guy. Have have heard some flat water freestyle guys like the D cut, because ski slides easier.
You may just have to expairment with the cut plate and see if you like it.