If you go to Jesse's HomeBrew Site, he has some tips listed there!
What I do is make a cardboard template of the hole locations. It might be easiest to use plain paper 1st and make a template for the holes, using scissors, etc. then after it looks good, make a cardboard template (Keep this Template, u may want to build another unit)
I don't use that type Enclosure but if it has foam in it like what I use, this should work:
Open up the Enclosure and lay the Camera in position on the Foam and trace around it with a Magic Marker. Remove the foam and cutout the camera hole, I use my Fillet Knife (cut inside the lines a little)
Place the camera inside the foam cutout and tape the Template to the Foam with it aligned properly to the cam, now replace the foam in the Enclosure with the Cam/ & Template in place.
Next, remove the Camera and use the Magic Marker to trace the Hole Locations on the Enclosure. Drill out the Holes and you're done......
To add a tip to Tinorns ideas.... Put the cam where you want it in the foam. Spread a SMALL amount of mineral oil, vaseline, etc, on the cams front around the lens opening. Close the 1120's cover (making sure it makes contact with the front of the cam) When you open the cover you should have a nice circle of oil on the inside of the lid as a marker for your hole cutting. Once you have the lens marked the other holes are just a matter of measuring.