I'm not sure how you would get on with non-circular wheelarches, or if the arches aren't centred about the wheels, but this is one mad tool!

Ruining arches on Mk1 Escorts for 35 years. I can't believe you have never seen one of these before.

A mate of mine got his arches rolled on his E30 M3 Cabby. They made a complete mess of them - he was devastated seeing as it was such a rare car. Apparently they used a proper rolling tool, garage said it was due to the heavy gauge steel that the shell was made out of. I dont know exact arch rolling model but the sales blurb makes it sound far too easy.

Arch rolling -

I've seen it done by jamming the small heavy glass coke bottle into the tyre/fender gap, and guiding the bottle as it rolls along the tyre as the car is pushed forward!

cheers

Fred WB