This script generates a teardrop shape at the appropriate angle to prevent overhangs greater than 45 degrees. The image shows a 45-degree rotation (no teardrop), a 60-degree rotation (shallow teardrop), and a 90-degree rotation (full 45-degree teardrop). This allows you to make holes at any angle that are as round as possible.

I actually came up with two solutions to this problem, because a bug was making my first solution take FOREVER to calculate. The second solution is still in the file, but has been commented-out.

The angle is in degrees, and is a rotation around the Y axis. You can then rotate around Z to point it in any direction. Rotation around Y or Z will cause the angle to be wrong. The module is intended to be used inside a difference statement.