I got a new flex fit front bumper from Ken’s Corvettes (they got bought out about a year ago) and the fitment was pretty poor. I think they all are, execpt of course if you’re going to replace yours with urethane. I had to fill about 1/4” on each side of my bumper. From what I was reading they all pretty much come from the same supplier. Mine was supposed to be the brand Ecklers uses so i expected good things. I guess these cars were hand layed so usually they don’t line up well.
I’d say Corvette Depot’s will probably be the same as the rest. As far as the mounting goes the urethane uses a metal retainer with threads and nuts that pintch it to the body. The flex fit or fiberglass use studs with nuts and don’t have the metal retainer that goes around it because it’s rigid enough.
Here are some pictures of mine and what it looks like underneath.