Excellent post. What type of carb and size was this test done under?
Also, it is not the amount of vacuum that matters, but what vacuum does it take to gain full advance from your vacuum cannister. Cannisters will vary of the rate of advance according to vacuum. So you may be able to pull more advance from a full vacuum source (i.e. manifold or under butterflies) than a ported source (above butterflies). So, you have to tune accordingly.