I have a friend that does cast concrete/cochina (sp?) stone.
He powers his frame cutter from a transformer and dimmer switch.
Said he would get shocked with the 120V unit.
About a 4" spring on the frame keeps it tight.
He uses masonite board for the profile shape and runs the wire along it.
He has 24" and 48" frames, I have always wondered if for a vehicle this would work:
Use a dowel on each end of an 6-8' piece of wire.
Have one person hold each end.
Guy in front follows old body.
Guy in rear follows end of boat tail shape.
Done in no time