This is an interesting experiment and I put some effort into one very similar, though smaller scale. I've always wanted to do something more inclusive and a little more serious though. I would really enjoy collaborating on this experiment.

This report from E-A-R Specialty Composites is one of the most accessible resources I found on the subject. It is written in very simple terms and is easy to read, but has some great details about how CLD works and what is important when considering them.

This report from Roush Industries is more technical but illustrates a simple method for determining the damping factor of a system graphically without using expensive software or hardware (you already have an accelerometer, just plug it into a spectrum analyzer like TrueRTA or REW).

You mention using a 'scope for measurements, but I believe the best method is a spectrum analyzer and calculating the damping factor as discussed in the article above. I have cleaned it up a bit and summarized the method in my experiment and it can be found here in the beginning of my build thread.

You mention using 22ga sheet metal. I'm not sure it would be the best test substrate. Most sheet metal in a car is much thicker, no? I realize that thicker material is substantially more expensive, but it is a very important factor. The effectiveness of a CLD is significantly related to the thickness of the substrate vs the thickness of the stiff backing (aluminum in most cases).