Mostly a hood will fit badly first time, but it takes time to get everything lined up. Just adding one washer under the rad at one side shifts everything around. You've got loads of adjustment - everywhere - before you have to resort to cutting and welding the hood. I spent ages trying to line up a hood which just wouldn't line up. It turned out the cheap repro grill shell wasn't symmetrical. One upper corner was a high tight curve while the other was a low drooping curve. A Vintique shell solved the problem.
I did not trim the replacement at all and followed your suggestions. The shop in question was definitely inexperienced and tested that theory on my car