Yeek. I'm out of my depth. Will read the link you sent more deeply at home tonight.
Although based on [a post by Marcel Veldhuizen](http://thorarin.net/blog/post/2013/02/21/Preserving-Stack-Trace.aspx), we will need a higher trust context, due to the internalness of `InternalPreserveStackTrace`.

To clarify, do you think this approach is more likely to run afoul of trust issues than the [original one you posted](https://github.com/xunit/xunit/blob/master/src/common/ExceptionExtensions.cs#L17)? We're trading access to a private field for access to an internal method.