+1 to the post above. I have done this as well. Send an MP3 of your basic track, and have them send YOU the pristine wav files of their contribution. You then import that back in to your original file. (Say your collaborator is a sax player wanting to just do a nice solo... Do they really need all source wavs & midi? probably not.) Now, IF your collaborator is to be expected to do all sorts of midi and audio editing and mixing, then you need to get the whole thing to them. PS, I have used bundle (*.bun or *CWB) files for years without problems, for what it's worth. Best - Ed