I installed quarter panels and patches for many years that way. There's a tool for an air hammer that makes a 1/2" wide flange in the old metal and allows a flush patch to be welded in. The Clecos are one way to attach the patch panel, but I prefer a set of long-reach welding Vise Grips every few inches if there's any way to use them. The fewer holes to weld up in a patch, the better, less heat distortion. The main advantage to replacing a big section like a quarter panel that way is that it doesn't require the OEM spot welds to be cut out, and there's less likelihood of getting a severe misalignment of the new panel.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!