Why bother using Hayden to be the body inside the Darth Vader suit? I mean, this is a fictional character with established presence and an established look. To my eye, coming off that table he just looked way too small. I know they gave him lifts to make him taller, but that didn't sell it for me. I could tell that this wasn't the "large" Darth Vader that we see in IV, V, and VI.
In the OT, Lucas didn't feel obliged to use Prowse's voice or to put James Earl into the costume. There was no hesitation to use a stunt performer for the lightsaber battles. When the time came to reveal his identity in ROTJ, Lucas didn't feel obliged to reveal Prowse. Lucas did what was necessary then to create the illusion of an imposing supervillian.
So what exactly was the point of creating a whole new downsized suit to fit Hayden into? Why not bring back Prowse or somebody equally large to fill those shoes for those scenes? I mean, he invited James Earl back. Why not somebody actually suitable to be the man behind the mask?