Sorry, I miss read your post. For sweep, I like a 6 or 10 pad on my sweep lead. Factoring in the 20 down test point, yes, you will be hitting the SDA with + 8db on the low end and 18 to 20db on the high end. As far as the C/N measurement, you are correct. The SDA is usually 1.5 to 2db lower than the 8591C.
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