Thanks for the feedback. I'm glad it's an improvement for you. I may also be able to suggest another way to narrow your metrics - by using
ignored tests.
If you right-click on your legacy test project and choose to ignore all the tests within it, the code coverage for these tests will be purged and they won't show inside the metrics window. If the tests run fast enough, you could simply ignore/unignore them as necessary to juggle your metrics reporting with your continuous execution of the old tests.
There are some rough plans to make improvements on engine modes that will allow them to configure criteria for metrics and code coverage, but this is still a way out at the moment. I hope that when these features are implemented they may give you further options in this area.