You can put the holes wherever you want, really. I don't have pre-drilled holes in my gaunts for the rockets and it works fine. Just make sure you get them done with matching screws. Wherever you put the screws is fine, it all gets covered up by the rocket when it's installed anyway. Totally up to you though on how you want to approach it.
Here's a link to how I did mine, scroll towards the bottom of the first post -
http://www.thedentedhelmet.com/f20/gauntlet-tutorial-utilizing-magnets-screws-too-51885/