The big hole is scary but the smaller ones (where the rivets/screws go) are where you can also mess up bad if not careful. If those smaller holes don't line up, the tach can point in the wrong direction and look bad or worse yet, you have to fill them and redrill. Measure twice, then measure twice again, then measure twice again, and then drill. I don't regret it at all, I love the look and it is one of the things that sets these cars apart from the crowd.