Wow Pete, pretty darn smick all the way out to the very edges that's for sure.
I cranked your 'Web' friendly version(not really friendly in any other terms
)... way up on my 24" mon checking for any star discrepancies around the edge......
Ahh, not a sign.
Beautifully consistent the whole field over.
The slight elongation could be as mentioned slight camera tilt, and at these extremes you are dealing with, more likely the prob.
But that is on the verge of nit picking I'd say.
I won't ask the price tag (that's rude
...)... well how much
But looks like you have yourself one hell of an express photon grabber
Can't wait to see the first serious image from this hunk of imaging magic
All the best
Rich