The trouble with the QHY9 on high speed is you get column artifacts too.
Definitely better to always use normal speed. I'm sure I've read somewhere on the QHY forums slow speed not necessary on modern drivers.
He's an example in Ha taken with high speed - columns were prominent in dark areas, particularly bottom right until I black clipped image a bit harder. Hardly a right-off though.
http://www.iceinspace.com.au/forum/a...e.php?a=187199
And final HaLRGB - all taken on slow speed. Veil is a reasonably bright object and astofest skies nice and dark
http://www.iceinspace.com.au/forum/a...e.php?a=188812