I tested the loudness penalty plugin in pro tools. Very cool, just open the plugin in audiosuite, select the file to test, render in a few seconds, then mouse over the youtube value to see how much it can be turned up without penalty. You can leave the plugin window open, select and render each song one by one to quickly check a list of songs. Would save a lot of time if I could do that in cubase!
In this screengrab, my mouse is hovering on the youtube score (shown as “–” to indicate that youtube won’t turn down the file), which causes the black rectangle to open saying how much the file can be turned up without penalty. The free website doesn’t have this feature.