Lee,
What happens when you reduce your aggressiveness down to 10%?
If you're within an arcminute of the pole (for the region of the sky in which you drift aligned), you might find that 50% at 600mm might be too much. This has certainly been the case for my FSQ/STL/G-11 combination. I've had to reduce my aggressiveness down to 1-1.5 to obtain a flat graph in MaxIm DL.
H
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