Thanks David.
First thing we did was matt-down the focuser/drawtube spacers with some ultra-flat black paint. These looked suspiciously shiny, despite the grooving/mini baffles.
The intention is almost solely galactic imagery with this one, so definitely not wanting a reducer, but after the test tonight, will decide if it needs any sort of field flattener. The CCDInspector result Lars provided showed around 30% curvature, though almost all of it at the periphery of the mirror. The central area looks nice, and it certainly is beautifully collimated (survived the road trip very well, thanks to Lars supreme packaging). Lars had tried a Tak flattener in it, to minimal effect.
The 4000 chip gives me a little hope for being outside the curve, as Richard suggests. I know my sadly departed ST8XE would have had no issue, with that tiny chip
