Now I know how to slow them down using the velocity/envelope technique, however, it doesn't change the length of the clip like it does in WMM. This can be crucial when trying to make extra space, or for overall aesthetic value (I like to speed up certain battle scenes during more intense parts of a song, for example).
Is there a counterpart to this in Vegas? I hope so, because it would be a shame to have to go back to using WMM for certain portions of my video, and thus certain parts of my video would suffer in quality.

Thank you and I hope this all made sense.