There is absolutely no reason not to enlarge from uncoated lenses.

http://www.apug.org/gallery/showphot...500&ppuser=124 was shot with an uncoated lens (zeiss Doppel-Amatar 150mm), so was http://www.apug.org/gallery/data/502/thumbs/Senja01.jpg (Angulon 210mm), http://www.apug.org/gallery/showphot...500&ppuser=124 (WA Rectilinear 3 1/4") and http://www.apug.org/gallery/showphot...500&ppuser=124 (Heliar 150mm).

I can assure you that all of these hold up very well under enlarging - and one of them is a crop of less than 1/4 of the film area.