I am selling my Aluminum ARE A.R.E. Contractor Utility Camper Shell. It's very secure.
I paid to have the windows custom upgraded with heavy duty steel mesh covers. What's nice is that they custom cut the steel mesh sheets to fit the windows, and smoothed off the edges. At the same time I paid to have all the rubber molding around the windows replaced.
What's also nice is that the shell can be removed easily since it's attached to the truck bed with rust free clamps. It's not sunk into the bed with old rusty bolts. You'll still need to bring a wrench or ratchet set to loosen the clamp screws.