Adrian - nice one! The 63mm 2.8 is incredible. I used to have terrible trouble with good corners past 16" from 35mm using 50mm lenses on my 10x8 enlarger. I had no idea what the trouble was but using the slightly longer 63mm sorted it... and what an incredible lens it is.
FWIW I directly compared a 50mm componon-S with a 50mm Durst Neonon (pentax made I believe) and while they were both sharp there was something about the tonality of the images, contrast etc with the Neonon and subsequent Nikkor 63mm (and 60mm Rodagon) that seemed much preferable to the Schneider. Not something I expected at all...
While I had issues with soft corners I actually used my 105mm for 35mm prints up to 20"! It produced immaculate sharpness wide open, which is more than I can say for the 80mm, which could not compete until F8.