I remained a little bit curious, so I Googled and an old thread here came up.....

http://www.apug.org/forums/forum41/3...cs-2000-a.html

So far as alignment goes, using a grain-magnifier you can see there is not much tolerance of mis-alignment as the distance to the easel increases. A normal spirit-level (potentially better than 0,5 degree) is marginal for alignment due to difficulty getting it on to the head, lens-mount and neg-stage and it might be better to use mirrors, or a test-neg and a corner focus-magnifier - or one of the laser alignment tools. Most good-quality enlargers have specific adjustment devices built in for micro alignment, but whether that is enough to combat toddler-assault is another question.