cheers,
you would expect Velcro to be weak....but it actually holds onto the box really well. Ive done a lot of driving since i put the box in and there has been no movement. You're idea of the metal clasps though would obviously kick Velcro's ass
But think of it this way, the Velcro doesn't do much at all, its actually the tight fit of the box that holds it in nicely.