Thanks for the feedback. I agree with your points. I have been tripped up by that before/after effect in the past and needed to reorder my code to deal with it.

I had expected a minimal overhead and 2% reflects this. Obviously, being an integer percentage, it doesn't exhibit a huge amount of precision. I usually run Benchmark several times, throw away any outliers and report an average or range. In this instance, all 3 or 4 runs produced 2%. It indicates an overhead but I wouldn't be setting my watch by it. :-)