Moved the MPCC out by another 1mm and I'm now pretty close. Field curvature has dropped a lot. I reckon another half a mill and I'll be spot-on. I'm about 1.5mm past the recommended spacing right now. Pretty chuffed with the primary cell. Collimation hasn't moved in a week now and I have been handling the scope back and forth a couple of times. Larger version
here.