The lens axis and negative have to be perpendicular. The baseboard alignment is secondary. At very big magnifications (16x20 etc) the baseboard can be an inch off and it will still be fine, however, the negative to lens alignment needs to be nearly as accurate as that of a 35mm camera body.
Originally Posted by gamincurieux
This may also help: http://www.apug.org/forums/forum41/5...endicular.html