Yes & No, how's that for an answer?
The reason you would want to warm the arch up is to help soften the paint to stop it cracking, not to soften the metal. Try to soften the metal & the paint will blister. I'd mask up the paintwork with a few layers of masking tape, just in case you miss the target, & then gently tap the arch from end to end with a panel hammer, repeating the process until the arch is where you want it.. Alternatively, use a bit of flat soft wood between the hammer & the arch & again, gently, gently tap it into place. I've done this a few times on upmarket cars & can't emphasize on doing it a bit at a time. If you take your time it should be ok, unless there's filler in the arch in which case it will crack. Be prepared for the fact that you might have to repair the 1/4's & paint the arch though. You're better off getting the right size back spacing on the wheels & fitting the right tyres tbhYou can buy a tool for doing this, but it's finding someone that'll lend it to you.hth.
cheers
Nige
