It is very difficult to get a perfect 90 deg bend in a short radius. The resulting Z-bend does USUALLY tend to enlarge the hole slightly. I don't see it causing a noticeable problem though any more than the silly notion of expanding/contracting Gold-N-Rods and the like. People just need to get over their belief that the average sport plane will be bothered by these things or that their "skills" will allow this to be detected noticeably.