quarter inch thick lexan, you can drill and tap holes into it from the edges. it's thick enough for a 10-32 to screw into it. cut out strips on a table saw, then cut them to to length (rectangles) with a band saw and a stop, and then make a little stop to hold them in your milling machine vice. do one step at a time in every part. it's easy to take them in and out of the vice, just set the depth stop on the mill and then you can drill one hole into each part. then move the stop and drill another hole, etc.
i can't think of a better way, but there might be something...anyway that's what i would do
