Druid: I respectfully disagree. Any time you use an instrument, there is inherent error in the instrument, and there is always inherent human error in reading any instrument, even a simple ruler. The more measurements you have to take, the more the error is compounded for any method. My method is not error free, i just feel it has less potential error than other methods if done correctly, and doesn't require a sensitive scale or precision ruler. But that's more science philosophy than anything.
That being said, whichever method you use, the error involved won't affect the results so much as to make you work your bow differently. All you really need is to get an idea whether your stave is low, high, or average for it's species. The difference would have to be dramatic to affect your treatment of the wood. I like the method i mentioned because it's quick, simple, and accurate enough for the bowyer's purposes. I haven't found it very difficult to find/cut pieces suitable-- from lumber or staves. I've only done SG testing twice, more out of curiosity than anything else.
I truly admire the work you do on your bows, they are always very impressive, so let me emphasize this as a respectful disagreement
But in the end I agree with JW, let's go shave some wood
