Inside its pretty solid and stout. The quarter panel goes on top of a factory rocker reinforcement for convertibles. We Learned that the hard way. The reinforcement is about 1/8 or so and it's very stout. We pry it down to put the new panel in and plug weld from the bottom, like it was originally. The only problem with that was that we couldn't pry it back up to to plug weld. So, after an hour of messing with it. We decided to just cut it off, put it where it needed and weld it back. Grind it smooth and can't tell it happened. I was happy to get it plug welded back. Even though it's on the bottom of the car, and will be covered with molding. I just feel better about it. Here is the patch welded in. Still needs some grinding and finishing. But its in. And will need a little filler. I'm surprised it's 18ga like the factory. It's solid. Just needs a couple hours of Clean up. But there's no pinholes. I'm happy. My buddy saved me a bunch of money. Fed him breakfast, and lunch, then we had beers