So, has anyone successfully shipped a bulky item like a qtr panel?

Steel or Glass?

GT racing boxes up there panels fenders etc in big cardboard boxes. Hank then packs most of GT's trash around the object to protect it, Then ships it to you.

So you get to dispose of all that stuff

Steel rear qtr panel.......

.........our company buys some parts that are packed along with pages of old McMaster-Carr catalogs...