I didn't want to butt in and answer something asked of you, but figured you used the right two part epoxy. The only good way to do it.
Funny story, I and a friend were headed over to the shop one evening, and the 'morning crew' of older guys had got in a hurry, and started to put the hood scoop on a '59 race truck, when we had our own plans of how to install it.
They had cut a hole, and riveted it from the top, then proceeded to feather it out with a bunch of resin and bondo. We arrived, and got to picking at it. Was cracking off already, so we proceeded to break it all back loose, and drill out the rivets. They had took a break or whatever, proud of their accomplishments, and then came back to the scoop they had just spent all morning putting on, now ripped off and laying on the floor. They were madder than hell, pissed off looks on their faces, just turned around and left without saying a word.
We sized the hole correctly, brought the scoop up from the bottom, and then used the correct two part epoxy. They eventually admitted it was a lot better than their boogered up mess, and its held without cracks for a whole lot of years. They were super pissed at the time though, lol.