I'm currious too, to know too why they changed the v11 sport frame. I have allways thought it was bad press. At the time the german magazines had bad things about it. And just at that moment Aprilia took the factory over, and wanted to make an end with te bad press. But they changed not only the frame angle/lenght. The front engine-frame mount is made stiffer, and more important, the rear part between engine and frame is made more stiff, with the extensions to the engine. That last change is the most important one I think.
My Daytona has a even one degree steeper angle then the v11 sport. And doesn't do strange things. But more things changed so this is no good comparison.