Well, the gap between the -16 and the -29 is pretty significant, you should be able to see that just about anywhere. The -23 is right in the middle, which is why it isn't as obvious of a difference. Where is it the biggest? The conditions you tested them in are at the high end. You might see a bigger difference in a CV SSP with minimal sea state, but inside the upper layer in a duct SSP is going to be about the same. I guess the point is that the -29 is only marginally better than the -23 and that the -23 is marginally better than the -16.
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