I'm trying to figure out how to hack the youtube module to add the string BEFORE the youtube U

I’m trying to figure out how to hack the youtube module to add the string <!–more–> BEFORE the youtube URL gets inserted. Everything that I try results in various errors. The reason that I am trying to do this is because I have added a plugin for automatically generating thumbnails that get inserted into the post preview image. I’m trying to cut down on page load from posting a lot of youtube videos.