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The sensor spacing is supposed to be 146mm according to Celestron, but that is to the end of the camera side threads of the reducer not the base of the threads, I have always though that was stupid, the measurement being given is to something that you cant directly measure when it is assembled!
Seems these work the opposite way to other reducer/correctors. Common wisdom is if you have comet tails pointing outwards then the spacing is too small and if you have a fishbowl effect with arcs around the edges, then it is too long, but this is taken from the Celestron blurb.
"Being outside of focus (too long) tends to produce elongated star images towards the edge"
I still suspect that your spacing was not quite right at F10 but the aberrations were not evident within the area of the chip. One other spacing impacting thing, I am not sure if the official camera backfocus measurement allows for the focus impact of the sensor chamber window.
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