I love it when a big-dicked top changes roles and takes a big cock up the butt. Tom Chase and Brad Patton are two great examples. Matt Rush, Nick Capra, Jason Kingsley, Rafael Alencar, Rafael Carreras, and DJ Chandler are other well hung tops who have "flipped" on film.
Here are some who have not flipped, but I would love to see them take the plunge: Arpad Miklos, Michael Lucas, Chad Hunt, Ben Andrews.