The only value that SGP cares about is the Mean HFR across the entire frame. Since we do whole frame auto focus, and don't weigh stars based on location, we would trend more towards the example on the right vs the left. Essentially we don't care where the stars are located, we use up to 300 stars across the entire frame and our autofocus will allways use the lowest average HFR produced across the entire image.
So unless you have a surplus of stars at the center, and very few around the middle, then I'm pretty sure our focus algorithm should get you what you're after, unless I'm missing something.
Thanks,
Jared