No probs mett - re your idea...I like the logic, but doesn't Sonar STILL save all the original audio in a project, even if a track is deleted? It is something I have noticed. In my case with the bass tracks. Deleted in the project, however the bass audio still resides in the audio folder...
 
EDIT: no it does not keep the audio for a deleted track as long as it is saved to a new folder. This indeed may be a better (easier/more efficient)  way.

Correct. SONAR does not delete audio on you (which is actually very important if you back-track in a project), but a current project file only points to the audio it needs. I popped open the biggest project I have with multitudes of audio files, and about 15 project versions... saving one project to a new folder only moved 4 audio files, so the "save as" is handy to keep track of which audio is for which project version.
 
I honestly have never cleaned audio off my machine just because of how cheap desktop storage has become, but definitely understand the issues with laptops. I am glad that option works for you.