I screwed the sleeve to the plastic on the underside and the top. Because the clearance was too tight to fit even the angle drill I had, I used a hot nail to make the pilot hole and then I used one of those s shaped screwdrivers to screw them in. I bet you could use a small rivet gun though, that would be even more secure.
I dont see how you could make it too hard to remove though since you dont even need a key to get it out, just a tiny phillips screwdriver.
Dustin