The last time I was at Ganassi I had noticed the fab guys had made their own step dies from nylon round stock, for doing their raised panel work, which made it possible to maneuver the panel and not get any die marks at all when doing curves, no stop/start marks, etc.
The way it was explained to me was that they could get real nice results and had a measure of "control", because of the "slip" of the rollers...the working of the metal could be carefully managed/controlled as the material was being fed into the rollers. This was on a motorized bead roller.