@User I am missing documentation about the magscale option in the mag(5) manpage: http://opencircuitdesign.com/magic/manpages/mag_manpage.html

Sorry, I never updated the man page for that. Since I modified magic to allow the underlying grid to be rescaled, it's necessary to specify in the .mag file what the actual scale of the coordinates is relative to the default lambda value. "magscale n d" means that the data are scaled by n/d relative to lambda.