Not sure how well you can tell from these pictures...
I learned the hard way by getting one ripped off my pack in the middle of nowhere. It left a web track until the battery died. I had purchased the $17 insurance and decided to replace it lieu of the long hard trek to go get it.
So for the second one, It's mounted on the top of my backpack. This gives it a good view of the sky. I used the elastic velcro strap provided, and wrapped it around the shoulder straps where they meet the top of the pack. Next I used a couple of Carabiners on different locations on the SPOT case, to attach to different straps on my pack. My thinking was if it got ripped off one section of the pack, it would have a second and third point of attachment. It's worked so far.
“Celebrate your success and stand strong when adversity hits, for when the storm clouds come in,
the Eagles soar while the small birds take cover.” Unknown