To add a slight bit of additional confusion to the discussion. Versalab includes instructions on resetting the alignment of the laser so it is exactly perpendicular to the base board. As described by IC Racer (sp?). Versalab also instructs using a rubber band to hold a piece of glass (it appears to be a microscope slide) to the barrel of the lens (Michael Mouse I think thought this up for them). My hands no longer being as clever as they were at one time I decided to use a screw in filter on the enlarging lens with a bit of paper stuck to the upper side. Ctein, in his fine book discusses the concentricity of the lens barrel with the lens elements - he found it was quite good. However, I found that a really cheapo filter didn't seem to have the glass concentric with the ring, so I tried a B&W filter I haven't been using. There was a significant difference. I emailed Versalab with this wonderful information and they responded they didn't think so. Didn't say why.

So there is my contribution to the great dancing angels controversy!