Today Ignacio and I drilled the holes in the aluminum side sheeting for the seismometer housing. A 3/8 drill bit (0.375" dia.) was used for the M8 screws (0.31" dia.) in order to leave some room for error.
Attachment 1: One of the side panels held against the frame.
Attachment 2: One of the smaller side panels to be used in the lid part of the housing. These will be attached to the top panel of the housing via hinges, so they did not require any holes along the top or bottom edges.