David,
Good sample of video from the XR520. Thanks for posting it. You mentioned the complexity of manual white balance with the L&M housing. Could you please share the steps involved? Presently, I am shooting with a Sony PD-170 in a Sea and Sea housing which (when set for one touch white balance) is merely the press of a button while pointing the camera at a white surface. Very interested in the process with this setup. I too am looking at a light travel rig for easy carry on. Travel to remote locations is getting more and more difficult and your new setup looks like it might just be the answer. Also, what depth were you shooting at in the various shots shown in your test footage? The reef shots? Even for a Youtube video, the results without lights look very good indeed.
Craig